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oeis

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1999-12-11 03:00:00
2025-04-25 01:21:50
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A001801
Coefficients of Legendre polynomials.
[ "3", "15", "105", "315", "6930", "18018", "90090", "218790", "2078505", "4849845", "22309287", "50702925", "1825305300", "4071834900", "18032411700", "39671305740", "347123925225", "755505013725", "3273855059475", "7064634602025", "121511715154830" ]
[ "nonn" ]
23
0
5
[ "A001790", "A001800", "A001801", "A004733", "A008316", "A100258" ]
[ "M3001", "N1216" ]
N. J. A. Sloane
2018-05-08T15:11:53
oeisdata/seq/A001/A001801.seq
c6fc62893fd50f43d43da7490553df27
A001802
Coefficients of Legendre polynomials.
[ "5", "35", "1260", "4620", "30030", "90090", "1021020", "2771340", "14549535", "37182145", "1487285800", "3650610600", "17644617900", "42075627300", "396713057400", "925663800600", "4281195077775", "9821565178425", "178970743251300", "405039050516100", "1822675727322450", "4079321865912150" ]
[ "nonn" ]
23
0
5
[ "A001802", "A100258" ]
[ "M3980", "N1649" ]
N. J. A. Sloane
2018-05-08T15:11:53
oeisdata/seq/A001/A001802.seq
93a2547217d7e8dc230f427a465142c2
A001803
Numerators in expansion of (1 - x)^(-3/2).
[ "1", "3", "15", "35", "315", "693", "3003", "6435", "109395", "230945", "969969", "2028117", "16900975", "35102025", "145422675", "300540195", "9917826435", "20419054425", "83945001525", "172308161025", "1412926920405", "2893136075115", "11835556670925" ]
[ "nonn", "frac" ]
110
0
5
[ "A001790", "A001800", "A001803", "A002011", "A002457", "A002596", "A004731", "A004735", "A005430", "A033876", "A046161", "A086116", "A086228", "A100258", "A161198", "A161199", "A161201", "A163590" ]
[ "M2986", "N1207" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001803.seq
d868563f306e52bc1038c99f3b8a8724
A001804
a(n) = n! * C(n,2).
[ "2", "18", "144", "1200", "10800", "105840", "1128960", "13063680", "163296000", "2195424000", "31614105600", "485707622400", "7933224499200", "137305808640000", "2510734786560000", "48373490221056000", "979563176976384000", "20801312169910272000", "462251381553561600000" ]
[ "nonn", "easy" ]
44
0
5
[ "A001804", "A001809", "A120434" ]
[ "M2109", "N0834" ]
N. J. A. Sloane
2021-12-19T10:04:29
oeisdata/seq/A001/A001804.seq
813d3a6b96ab1024399f7c1dc0cdfaf5
A001805
a(n) = n! * binomial(n,3).
[ "6", "96", "1200", "14400", "176400", "2257920", "30481920", "435456000", "6586272000", "105380352000", "1780927948800", "31732897996800", "594991837440000", "11716762337280000", "241867451105280000", "5224336943874048000", "117874102296158208000", "2773508289321369600000" ]
[ "nonn" ]
39
0
5
[ "A001805", "A021012" ]
[ "M4291", "N1794" ]
N. J. A. Sloane
2022-09-08T08:44:29
oeisdata/seq/A001/A001805.seq
91a876ff8138c6b0df69cb14ffa517a5
A001806
a(n) = n! * binomial(n,4).
[ "24", "600", "10800", "176400", "2822400", "45722880", "762048000", "13172544000", "237105792000", "4452319872000", "87265469491200", "1784975512320000", "38079477596160000", "846536078868480000", "19591263539527680000", "471496409184632832000", "11787410229615820800000" ]
[ "nonn" ]
35
0
5
[ "A001806", "A021012" ]
[ "M5165", "N2242" ]
N. J. A. Sloane
2022-09-08T08:44:29
oeisdata/seq/A001/A001806.seq
2490deeb8cfdfb7e33fa6edd9ae8e26b
A001807
a(n) = n! * binomial(n,5).
[ "120", "4320", "105840", "2257920", "45722880", "914457600", "18441561600", "379369267200", "8014175769600", "174530938982400", "3926946127104000", "91390746230784000", "2200993805058048000", "54855537910677504000", "1414489227553898496000", "37719712734770626560000" ]
[ "nonn" ]
36
0
5
[ "A001807", "A021012" ]
[ "M5380", "N2337" ]
N. J. A. Sloane
2022-09-08T08:44:29
oeisdata/seq/A001/A001807.seq
952ce2b461435dfb619291241f128fd5
A001808
Expansion of 1/((1+x)*(1-x)^12).
[ "1", "11", "67", "297", "1068", "3300", "9076", "22748", "52834", "115126", "237590", "467842", "884236", "1611908", "2845492", "4880668", "8157227", "13316953", "21280337", "33346963", "51325352", "77699128", "115837592", "170260168", "246965732", "353839564", "501152588", "702169700", "973886344", "1337915096" ]
[ "nonn", "easy", "changed" ]
31
0
5
[ "A001808", "A112465" ]
null
N. J. A. Sloane
2025-04-21T10:47:49
oeisdata/seq/A001/A001808.seq
52bde7a9586480f9141b30252c1c0206
A001809
a(n) = n! * n(n-1)/4.
[ "0", "0", "1", "9", "72", "600", "5400", "52920", "564480", "6531840", "81648000", "1097712000", "15807052800", "242853811200", "3966612249600", "68652904320000", "1255367393280000", "24186745110528000", "489781588488192000", "10400656084955136000", "231125690776780800000", "5364548928029491200000" ]
[ "nonn", "easy", "nice", "eigen" ]
120
0
5
[ "A001620", "A001809", "A008302", "A034968", "A053495", "A064038", "A099285" ]
[ "M4649", "N1989" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001809.seq
fbf2125291e348bc2a69942a2484a8b5
A001810
a(n) = n!*n*(n-1)*(n-2)/36.
[ "0", "0", "0", "1", "16", "200", "2400", "29400", "376320", "5080320", "72576000", "1097712000", "17563392000", "296821324800", "5288816332800", "99165306240000", "1952793722880000", "40311241850880000", "870722823979008000", "19645683716026368000", "462251381553561600000", "11325158848062259200000" ]
[ "nonn" ]
52
0
5
[ "A001113", "A001620", "A001810", "A053495", "A091725", "A099285", "A263771" ]
[ "M5019", "N2163" ]
N. J. A. Sloane
2022-09-08T08:44:29
oeisdata/seq/A001/A001810.seq
e5d160ee5cadaa297539b0fccb0d16d1
A001811
Coefficients of Laguerre polynomials.
[ "1", "25", "450", "7350", "117600", "1905120", "31752000", "548856000", "9879408000", "185513328000", "3636061228800", "74373979680000", "1586644899840000", "35272336619520000", "816302647480320000", "19645683716026368000", "491142092900659200000", "12740803704070041600000" ]
[ "nonn", "easy" ]
42
0
5
[ "A001113", "A001620", "A001811", "A053495", "A091725", "A099285" ]
[ "M5185", "N2253" ]
N. J. A. Sloane
2022-05-02T08:31:38
oeisdata/seq/A001/A001811.seq
537d10ae8eab7120e871aeebbb58ae08
A001812
Coefficients of Laguerre polynomials.
[ "1", "36", "882", "18816", "381024", "7620480", "153679680", "3161410560", "66784798080", "1454424491520", "32724551059200", "761589551923200", "18341615042150400", "457129482588979200", "11787410229615820800", "314330939456421888000", "8663746518767628288000", "246661959710796005376000" ]
[ "nonn" ]
49
0
5
[ "A001113", "A001620", "A001812", "A021009", "A091725", "A099285" ]
[ "M5257", "N2289" ]
N. J. A. Sloane
2024-12-27T03:49:13
oeisdata/seq/A001/A001812.seq
5e04ae46b9f3478bffe424a291701a9e
A001813
Quadruple factorial numbers: a(n) = (2n)!/n!.
[ "1", "2", "12", "120", "1680", "30240", "665280", "17297280", "518918400", "17643225600", "670442572800", "28158588057600", "1295295050649600", "64764752532480000", "3497296636753920000", "202843204931727360000", "12576278705767096320000", "830034394580628357120000", "58102407620643984998400000" ]
[ "nonn", "easy", "nice" ]
276
0
5
[ "A000085", "A000108", "A000142", "A000165", "A000407", "A000680", "A000984", "A001147", "A001700", "A001813", "A006882", "A007696", "A008275", "A008276", "A008545", "A010050", "A037224", "A047055", "A047657", "A048854", "A052714", "A052734", "A059344", "A066325", "A084947", "A084948", "A084949", "A094216", "A099174", "A122670", "A123023", "A135401", "A144828", "A221953", "A221954", "A221955", "A297708" ]
[ "M2040", "N0808" ]
N. J. A. Sloane
2025-01-22T08:52:11
oeisdata/seq/A001/A001813.seq
eacf3e3cc1cd7bbcf81be05154d135c8
A001814
Coefficient of H_2 when expressing x^{2n} in terms of Hermite polynomials H_m.
[ "1", "12", "180", "3360", "75600", "1995840", "60540480", "2075673600", "79394515200", "3352212864000", "154872234316800", "7771770303897600", "420970891461120000", "24481076457277440000", "1521324036987955200000", "100610229646136770560000" ]
[ "nonn" ]
38
0
5
[ "A001814", "A001879", "A005430", "A048854", "A067147" ]
[ "M4875", "N2088" ]
N. J. A. Sloane
2022-09-08T08:44:29
oeisdata/seq/A001/A001814.seq
72c43917739d53a74ffd6abdaffdbda8
A001815
a(n) = binomial(n,2) * 2^(n-1).
[ "0", "0", "2", "12", "48", "160", "480", "1344", "3584", "9216", "23040", "56320", "135168", "319488", "745472", "1720320", "3932160", "8912896", "20054016", "44826624", "99614720", "220200960", "484442112", "1061158912", "2315255808", "5033164800", "10905190400", "23555211264", "50734301184", "108984795136" ]
[ "nonn", "easy" ]
126
0
5
[ "A001788", "A001815", "A089264", "A090802" ]
[ "M2021", "N0799" ]
N. J. A. Sloane
2022-09-08T08:44:29
oeisdata/seq/A001/A001815.seq
3a63197445bce134815bbec742283627
A001816
Coefficients of x^n in Hermite polynomial H_{n+4}.
[ "12", "120", "720", "3360", "13440", "48384", "161280", "506880", "1520640", "4392960", "12300288", "33546240", "89456640", "233963520", "601620480", "1524105216", "3810263040", "9413591040", "23011000320", "55710842880", "133706022912", "318347673600", "752458137600", "1766640844800", "4122161971200" ]
[ "nonn", "easy" ]
34
0
5
[ "A001816", "A003472", "A060821" ]
[ "M4862", "N2078" ]
N. J. A. Sloane, Simon Plouffe
2025-01-17T09:39:04
oeisdata/seq/A001/A001816.seq
753a21016e8132b931d46e40f1749840
A001817
G.f.: Sum_{n>0} x^n/(1-x^(3n)) = Sum_{n>=0} x^(3n+1)/(1-x^(3n+1)).
[ "1", "1", "1", "2", "1", "1", "2", "2", "1", "2", "1", "2", "2", "2", "1", "3", "1", "1", "2", "3", "2", "2", "1", "2", "2", "2", "1", "4", "1", "2", "2", "3", "1", "2", "2", "2", "2", "2", "2", "4", "1", "2", "2", "3", "1", "2", "1", "3", "3", "3", "1", "4", "1", "1", "2", "4", "2", "2", "1", "3", "2", "2", "2", "4", "2", "2", "2", "3", "1", "4", "1", "2", "2", "2", "2", "4", "2", "2", "2", "5", "1", "2", "1", "4", "2", "2", "1", "4", "1", "2", "4", "3", "2", "2", "2", "3", "2", "3", "1", "5", "1", "2", "2", "4", "2" ]
[ "nonn", "easy" ]
51
0
5
[ "A001620", "A001817", "A001822", "A002324", "A035191", "A051731", "A256425" ]
null
N. J. A. Sloane
2023-11-25T04:44:37
oeisdata/seq/A001/A001817.seq
d3116a9c50dc2ba6e84971e55f8aa0fd
A001818
Squares of double factorials: (1*3*5*...*(2n-1))^2 = ((2*n-1)!!)^2.
[ "1", "1", "9", "225", "11025", "893025", "108056025", "18261468225", "4108830350625", "1187451971330625", "428670161650355625", "189043541287806830625", "100004033341249813400625", "62502520838281133375390625", "45564337691106946230659765625", "38319607998220941779984862890625" ]
[ "nonn", "easy", "nice" ]
155
0
5
[ "A001147", "A001818", "A002454", "A008956", "A012248", "A111595", "A197037" ]
[ "M4669", "N1997" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001818.seq
740b22c445ceb02396e620c39f952244
A001819
Central factorial numbers: second right-hand column of triangle A008955.
[ "0", "1", "5", "49", "820", "21076", "773136", "38402064", "2483133696", "202759531776", "20407635072000", "2482492033152000", "359072203696128000", "60912644957448192000", "11977654199703478272000", "2702572249389834608640000" ]
[ "nonn", "easy", "nice" ]
80
0
5
[ "A000254", "A001044", "A001819", "A002455", "A007406", "A007407", "A008955", "A024167", "A066989", "A142995", "A162990" ]
[ "M4008", "N1661" ]
N. J. A. Sloane
2020-07-08T20:38:06
oeisdata/seq/A001/A001819.seq
a4e41830a947ddda00192ace22fd7660
A001820
Central factorial numbers: 2nd subdiagonal of A008955.
[ "1", "14", "273", "7645", "296296", "15291640", "1017067024", "84865562640", "8689315795776", "1071814846360896", "156823829909121024", "26862299458337581056", "5325923338791614078976", "1210310405427816646041600", "312542036038910895995289600", "91018216923341770801874534400" ]
[ "nonn" ]
45
0
5
[ "A001820", "A008955", "A049033" ]
[ "M4952", "N2121" ]
N. J. A. Sloane
2025-01-13T10:44:00
oeisdata/seq/A001/A001820.seq
181c9b957fb11f737ab29fbd480a1908
A001821
Central factorial numbers: 3rd subdiagonal of A008955.
[ "1", "30", "1023", "44473", "2475473", "173721912", "15088541896", "1593719752240", "201529405816816", "30092049283982400", "5242380158902146624", "1054368810603158319360", "242558905724502235934976", "63305390270900389045395456", "18607799824329123330114576384" ]
[ "nonn" ]
43
0
5
[ "A001821", "A008955" ]
[ "M5215", "N2269" ]
N. J. A. Sloane
2025-01-13T10:43:02
oeisdata/seq/A001/A001821.seq
9430b8b26f8c4d628db691e7d45f20b4
A001822
Expansion of Sum_{n>=0} x^(3n+2)/(1-x^(3n+2)).
[ "0", "1", "0", "1", "1", "1", "0", "2", "0", "2", "1", "1", "0", "2", "1", "2", "1", "1", "0", "3", "0", "2", "1", "2", "1", "2", "0", "2", "1", "2", "0", "3", "1", "2", "2", "1", "0", "2", "0", "4", "1", "2", "0", "3", "1", "2", "1", "2", "0", "3", "1", "2", "1", "1", "2", "4", "0", "2", "1", "3", "0", "2", "0", "3", "2", "2", "0", "3", "1", "4", "1", "2", "0", "2", "1", "2", "2", "2", "0", "5", "0", "2", "1", "2", "2", "2", "1", "4", "1", "2", "0", "3", "0", "2", "2", "3", "0", "3", "1", "4", "1", "2", "0", "4", "2" ]
[ "nonn", "easy" ]
42
0
5
[ "A000005", "A001620", "A001817", "A001822", "A002324", "A035191", "A256843" ]
null
N. J. A. Sloane
2023-11-25T08:02:02
oeisdata/seq/A001/A001822.seq
2add9ae3ebc709a8793fb760a1883f72
A001823
Central factorial numbers: column 2 in triangle A008956.
[ "0", "9", "259", "1974", "8778", "28743", "77077", "179452", "375972", "725781", "1312311", "2249170", "3686670", "5818995", "8892009", "13211704", "19153288", "27170913", "37808043", "51708462", "69627922", "92446431", "121181181", "157000116", "201236140", "255401965", "321205599", "400566474", "495632214" ]
[ "nonn" ]
47
0
5
[ "A001823", "A008956", "A181888" ]
[ "M4671", "N1998" ]
N. J. A. Sloane
2022-04-13T13:25:16
oeisdata/seq/A001/A001823.seq
bfdc30e22754f4ede10832ae6ca07827
A001824
Central factorial numbers: 1st subdiagonal of A008956.
[ "1", "10", "259", "12916", "1057221", "128816766", "21878089479", "4940831601000", "1432009163039625", "518142759828635250", "228929627246078500875", "121292816354463333793500", "75908014254880833434338125", "55399444912646408707007883750", "46636497509226736668824289999375" ]
[ "nonn", "easy", "nice" ]
55
0
5
[ "A001824", "A001825", "A002455", "A008956", "A049033" ]
[ "M4749", "N2031" ]
N. J. A. Sloane
2025-01-13T10:23:10
oeisdata/seq/A001/A001824.seq
5b030342eb05696d8d91380b45f1bf7a
A001825
Central factorial numbers: 2nd subdiagonal of A008956.
[ "1", "35", "1974", "172810", "21967231", "3841278805", "886165820604", "261042753755556", "95668443268795341", "42707926241367380631", "22821422608929422854674", "14384681946935352617964750", "10562341153570752891930640875" ]
[ "nonn" ]
32
0
5
[ "A001824", "A001825", "A002455", "A008956", "A049033" ]
[ "M5250", "N2284" ]
N. J. A. Sloane
2025-01-13T10:46:38
oeisdata/seq/A001/A001825.seq
9c2b86586839251a829b473bee095f21
A001826
Number of divisors of n of the form 4k+1.
[ "1", "1", "1", "1", "2", "1", "1", "1", "2", "2", "1", "1", "2", "1", "2", "1", "2", "2", "1", "2", "2", "1", "1", "1", "3", "2", "2", "1", "2", "2", "1", "1", "2", "2", "2", "2", "2", "1", "2", "2", "2", "2", "1", "1", "4", "1", "1", "1", "2", "3", "2", "2", "2", "2", "2", "1", "2", "2", "1", "2", "2", "1", "3", "1", "4", "2", "1", "2", "2", "2", "1", "2", "2", "2", "3", "1", "2", "2", "1", "2", "3", "2", "1", "2", "4", "1", "2", "1", "2", "4", "2", "1", "2", "1", "2", "1", "2", "2", "3", "3", "2", "2", "1", "2", "4" ]
[ "nonn", "easy" ]
35
0
5
[ "A001227", "A001620", "A001826", "A001842", "A256778" ]
null
N. J. A. Sloane
2023-11-25T04:33:58
oeisdata/seq/A001/A001826.seq
1daba334894f7dc6c801d4fbce588a14
A001827
Related to graded partially ordered sets.
[ "1", "4", "22", "166", "1726", "24814", "494902", "13729846", "531077086", "28697950174", "2170176736102", "230007989092006", "34211282155446286", "7149766552058591374", "2101690590380890192342", "869808621195903097079446", "507261036269544624540347326" ]
[ "nonn" ]
32
0
5
[ "A000684", "A001827", "A001828", "A001829", "A001830", "A047863", "A361950" ]
[ "M3591", "N1456" ]
N. J. A. Sloane
2023-03-31T14:09:29
oeisdata/seq/A001/A001827.seq
ec3fda9395d729c7ead52819b1b1797f
A001828
Related to graded partially ordered sets.
[ "1", "5", "33", "287", "3309", "50975", "1058493", "29885567", "1156711869", "61815727295", "4589058616413", "475576073939807", "69061902766811229", "14093318360697120095", "4049931601653596366013", "1641314561238334948886207", "939097032426474389539281789" ]
[ "nonn" ]
35
0
5
[ "A000684", "A001827", "A001828", "A001829", "A001830", "A047863", "A361950" ]
[ "M3971", "N1641" ]
N. J. A. Sloane
2023-03-31T14:09:38
oeisdata/seq/A001/A001828.seq
dc227b644a00720fcabe5eae4c8b9807
A001829
Related to graded partially ordered sets.
[ "1", "6", "46", "450", "5650", "91866", "1957066", "55363650", "2109599650", "109773407466", "7894945079386", "792252362302770", "111671194813402930", "22202849561274787866", "6241728810901739517226", "2484011055161613143144610", "1400187830319472451472442690" ]
[ "nonn" ]
34
0
5
[ "A000684", "A001827", "A001828", "A001829", "A001830", "A047863", "A361950" ]
[ "M4252", "N1776" ]
N. J. A. Sloane
2023-03-31T14:09:45
oeisdata/seq/A001/A001829.seq
98e316e045fde01d0226d1932d65240b
A001830
Related to graded partially ordered sets.
[ "1", "7", "61", "661", "8953", "152917", "3334921", "94354981", "3528929353", "177999003157", "12340001650921", "1194005625114661", "162936187792764073", "31536761103831315157", "8677703806537883683081", "3395880602480076153665701", "1889190751946097573211698313" ]
[ "nonn" ]
37
0
5
[ "A000684", "A001827", "A001828", "A001829", "A001830", "A047863", "A361950" ]
[ "M4439", "N1877" ]
N. J. A. Sloane
2024-05-19T08:40:40
oeisdata/seq/A001/A001830.seq
9c6ae305615920ef7312fbaaf8d31b07
A001831
Number of labeled graded partially ordered sets with n elements of height at most 1.
[ "1", "1", "3", "13", "87", "841", "11643", "227893", "6285807", "243593041", "13262556723", "1014466283293", "109128015915207", "16521353903210521", "3524056001906654763", "1059868947134489801413", "449831067019305308555487", "269568708630308018001547681", "228228540531327778410439620963" ]
[ "nonn", "nice" ]
60
0
5
[ "A001831", "A001833", "A002031", "A047863", "A048194", "A052296", "A052332", "A135753", "A135754" ]
[ "M2956", "N1194" ]
N. J. A. Sloane
2021-03-08T12:01:17
oeisdata/seq/A001/A001831.seq
23978c435cdd365d4a614ed1fe895db1
A001832
Number of labeled connected bipartite graphs on n nodes.
[ "1", "1", "3", "19", "195", "3031", "67263", "2086099", "89224635", "5254054111", "426609529863", "47982981969979", "7507894696005795", "1641072554263066471", "502596525992239961103", "216218525837808950623459", "130887167385831881114006475", "111653218763166828863141636911" ]
[ "nonn", "nice", "easy" ]
63
0
5
[ "A001832", "A002031", "A005142", "A047863", "A047864", "A228861" ]
[ "M3063", "N1241" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001832.seq
1fa57f3febe5ef44ae3d7d658edbcedd
A001833
Number of labeled graded partially ordered sets with n elements.
[ "1", "1", "3", "19", "219", "3991", "106623", "3964339", "199515459", "13399883551", "1197639892983", "143076298623259", "23053861370437659", "5062745845287855271", "1530139311543346178223", "641441466132460086890179", "375107113287994040621904819", "307244526491924695346004951151", "353511145615118063468292270299943" ]
[ "nonn" ]
41
0
5
[ "A001831", "A001833", "A223911", "A228551", "A361920", "A361951" ]
[ "M3067", "N1243" ]
N. J. A. Sloane
2023-04-01T15:49:02
oeisdata/seq/A001/A001833.seq
5ce7a2fab5717764c67d1f1b6cfed232
A001834
a(0) = 1, a(1) = 5, a(n) = 4*a(n-1) - a(n-2).
[ "1", "5", "19", "71", "265", "989", "3691", "13775", "51409", "191861", "716035", "2672279", "9973081", "37220045", "138907099", "518408351", "1934726305", "7220496869", "26947261171", "100568547815", "375326930089", "1400739172541", "5227629760075", "19509779867759", "72811489710961", "271736178976085" ]
[ "nonn", "easy", "nice" ]
210
0
5
[ "A001352", "A001353", "A001834", "A001835", "A002531", "A026150", "A049310", "A082841", "A086386", "A094347", "A100047" ]
[ "M3890", "N1598" ]
N. J. A. Sloane
2025-01-05T19:51:32
oeisdata/seq/A001/A001834.seq
4d754603783e7d4e42dcf4312a136fb0
A001835
a(n) = 4*a(n-1) - a(n-2), with a(0) = 1, a(1) = 1.
[ "1", "1", "3", "11", "41", "153", "571", "2131", "7953", "29681", "110771", "413403", "1542841", "5757961", "21489003", "80198051", "299303201", "1117014753", "4168755811", "15558008491", "58063278153", "216695104121", "808717138331", "3018173449203", "11263976658481" ]
[ "nonn", "easy", "nice", "changed" ]
313
0
5
[ "A001353", "A001519", "A001542", "A001835", "A002530", "A003699", "A005246", "A006253", "A048788", "A052530", "A079935", "A082841", "A096147", "A099390", "A101265", "A103997", "A125077" ]
[ "M2894", "N1160" ]
N. J. A. Sloane
2025-04-16T05:24:50
oeisdata/seq/A001/A001835.seq
31caed656eae3417825768db0a6906b5
A001836
Numbers k such that phi(2k-1) < phi(2k), where phi is Euler's totient function A000010.
[ "53", "83", "158", "263", "293", "368", "578", "683", "743", "788", "878", "893", "908", "998", "1073", "1103", "1208", "1238", "1268", "1403", "1418", "1502", "1523", "1658", "1733", "1838", "1943", "1964", "2048", "2063", "2153", "2228", "2243", "2258", "2363", "2393", "2423", "2468", "2558", "2573", "2633", "2657", "2678" ]
[ "nonn", "nice" ]
49
0
5
[ "A000010", "A001836", "A001837" ]
[ "M5429", "N2359" ]
N. J. A. Sloane
2023-09-23T23:34:02
oeisdata/seq/A001/A001836.seq
10f144bfb29d4c9835e5f97ea855214e
A001837
Numbers k such that phi(2k+1) < phi(2k).
[ "157", "262", "367", "412", "472", "487", "577", "682", "787", "877", "892", "907", "997", "1072", "1207", "1237", "1312", "1402", "1522", "1567", "1627", "1657", "1732", "1852", "1942", "2047", "2062", "2152", "2194", "2257", "2362", "2437", "2467", "2557", "2572", "2677", "2722", "2782" ]
[ "nonn" ]
31
0
5
[ "A000010", "A001837" ]
[ "M5406", "N2349" ]
N. J. A. Sloane
2022-02-04T02:02:01
oeisdata/seq/A001/A001837.seq
26726243040ffdbd2c70349bd4282b9b
A001838
Numbers k such that phi(k+2) = phi(k) + 2.
[ "3", "5", "6", "11", "12", "14", "17", "18", "20", "29", "41", "44", "59", "62", "71", "92", "101", "107", "116", "137", "149", "164", "179", "191", "197", "212", "227", "239", "254", "269", "281", "311", "332", "347", "356", "419", "431", "452", "461", "521", "524", "569", "599", "617", "641", "659", "692", "716", "764", "809", "821", "827", "857", "881", "932", "956" ]
[ "nonn", "nice" ]
52
0
5
[ "A001838", "A050472", "A050473", "A056853" ]
[ "M2397", "N0951" ]
N. J. A. Sloane
2023-09-24T00:04:49
oeisdata/seq/A001/A001838.seq
5263a95bbb969c1fb16c0815fad69111
A001839
The coding-theoretic function A(n,4,3).
[ "0", "0", "1", "1", "2", "4", "7", "8", "12", "13", "17", "20", "26", "28", "35", "37", "44", "48", "57", "60", "70", "73", "83", "88", "100", "104", "117", "121", "134", "140", "155", "160", "176", "181", "197", "204", "222", "228", "247", "253", "272", "280", "301", "308", "330", "337", "359", "368", "392", "400", "425", "433", "458", "468", "495", "504", "532", "541", "569", "580", "610", "620", "651", "661", "692", "704", "737", "748", "782", "793" ]
[ "nonn", "easy", "nice" ]
75
0
5
[ "A001839", "A001843", "A011975", "A060407" ]
[ "M1032", "N0389" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001839.seq
7ac1b9e39b515f16e34c554cd585d26c
A001840
Expansion of g.f. x/((1 - x)^2*(1 - x^3)).
[ "0", "1", "2", "3", "5", "7", "9", "12", "15", "18", "22", "26", "30", "35", "40", "45", "51", "57", "63", "70", "77", "84", "92", "100", "108", "117", "126", "135", "145", "155", "165", "176", "187", "198", "210", "222", "234", "247", "260", "273", "287", "301", "315", "330", "345", "360", "376", "392", "408", "425", "442", "459", "477", "495", "513", "532", "551", "570", "590" ]
[ "nonn", "easy", "nice" ]
238
0
5
[ "A000031", "A000217", "A001037", "A001318", "A001399", "A001840", "A007052", "A007304", "A008748", "A011782", "A011847", "A014311", "A014612", "A045943", "A051168", "A058937", "A069905", "A130205", "A156040", "A218004", "A258708", "A337453", "A337483", "A337484" ]
[ "M0638", "N0233" ]
N. J. A. Sloane
2025-03-04T07:55:25
oeisdata/seq/A001/A001840.seq
a3ec0e1fe3c3b5127eb5a670d4be22cf
A001841
Related to Zarankiewicz's problem.
[ "3", "5", "10", "14", "21", "26", "36", "43", "55", "64", "78", "88", "105", "117", "136", "150", "171", "186", "210", "227", "253", "272", "300", "320", "351", "373", "406", "430", "465", "490", "528", "555", "595", "624", "666", "696", "741" ]
[ "nonn" ]
37
0
5
null
[ "M2460", "N0977" ]
N. J. A. Sloane
2022-04-13T13:25:16
oeisdata/seq/A001/A001841.seq
47e68f025c73440ab18d14feb7e29ebb
A001842
Expansion of Sum_{n>=0} x^(4*n+3)/(1 - x^(4*n+3)).
[ "0", "0", "0", "1", "0", "0", "1", "1", "0", "1", "0", "1", "1", "0", "1", "2", "0", "0", "1", "1", "0", "2", "1", "1", "1", "0", "0", "2", "1", "0", "2", "1", "0", "2", "0", "2", "1", "0", "1", "2", "0", "0", "2", "1", "1", "2", "1", "1", "1", "1", "0", "2", "0", "0", "2", "2", "1", "2", "0", "1", "2", "0", "1", "3", "0", "0", "2", "1", "0", "2", "2", "1", "1", "0", "0", "3", "1", "2", "2", "1", "0", "2", "0", "1", "2", "0", "1" ]
[ "nonn", "easy" ]
47
0
5
[ "A001227", "A001620", "A001826", "A001842", "A072437", "A256846" ]
null
N. J. A. Sloane
2023-11-25T04:44:17
oeisdata/seq/A001/A001842.seq
ea6573086bfa2d47b647f9e217c188c6
A001843
The coding-theoretic function A(n,4,4).
[ "1", "1", "3", "7", "14", "18", "30", "35", "51", "65", "91", "105", "140", "157", "198", "228", "285", "315", "385", "419", "498", "550", "650", "702", "819", "877", "1005", "1085", "1240", "1320", "1496", "1583", "1773", "1887", "2109", "2223", "2470", "2593", "2856", "3010", "3311", "3465", "3795", "3959", "4308", "4508", "4900", "5100", "5525", "5737" ]
[ "nonn", "nice", "easy" ]
43
0
5
null
[ "M2644", "N1052" ]
N. J. A. Sloane
2022-09-25T07:19:28
oeisdata/seq/A001/A001843.seq
738c86ca4ae4c237761a6b1aae13eeb4
A001844
Centered square numbers: a(n) = 2*n*(n+1)+1. Sums of two consecutive squares. Also, consider all Pythagorean triples (X, Y, Z=Y+1) ordered by increasing Z; then sequence gives Z values.
[ "1", "5", "13", "25", "41", "61", "85", "113", "145", "181", "221", "265", "313", "365", "421", "481", "545", "613", "685", "761", "841", "925", "1013", "1105", "1201", "1301", "1405", "1513", "1625", "1741", "1861", "1985", "2113", "2245", "2381", "2521", "2665", "2813", "2965", "3121", "3281", "3445", "3613", "3785", "3961", "4141", "4325", "4513" ]
[ "nonn", "easy", "nice" ]
558
0
5
[ "A000217", "A000290", "A000982", "A001263", "A001788", "A001844", "A002061", "A004431", "A005408", "A005448", "A005891", "A005900", "A008288", "A008586", "A008844", "A016754", "A027862", "A046092", "A048395", "A051890", "A055096", "A056106", "A069480", "A078475", "A080827", "A101096", "A127876", "A128064", "A129312", "A132778", "A147973", "A153869", "A240876", "A251599", "A254373" ]
[ "M3826", "N1567" ]
N. J. A. Sloane
2025-04-06T22:00:38
oeisdata/seq/A001/A001844.seq
6cf69509da0197fee069053d745407bb
A001845
Centered octahedral numbers (crystal ball sequence for cubic lattice).
[ "1", "7", "25", "63", "129", "231", "377", "575", "833", "1159", "1561", "2047", "2625", "3303", "4089", "4991", "6017", "7175", "8473", "9919", "11521", "13287", "15225", "17343", "19649", "22151", "24857", "27775", "30913", "34279", "37881", "41727", "45825", "50183", "54809", "59711", "64897", "70375", "76153", "82239" ]
[ "nonn", "easy", "nice" ]
182
0
5
[ "A001845", "A001846", "A001847", "A001848", "A002412", "A005893", "A005894", "A005897", "A005898", "A005899", "A005901", "A005902", "A005917", "A007202", "A007899", "A008137", "A008288", "A008412", "A010001", "A013609", "A014820", "A016061", "A049480", "A057813", "A063488", "A063489", "A063490", "A063491", "A063492", "A063493", "A063494", "A063495", "A063496", "A240876", "A299254", "A299255", "A299256", "A299257", "A299258", "A299259", "A299260", "A299261", "A299262", "A299263", "A299264", "A299265", "A299266", "A299267", "A299268", "A299269", "A299272", "A299273", "A299274", "A299275", "A299276", "A299277", "A299278", "A299279", "A299280", "A299281", "A299282", "A299283", "A299284", "A299285", "A299286", "A299287", "A299288", "A299289", "A299290", "A299291", "A299292" ]
[ "M4384", "N1844" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001845.seq
d66edd814686f3bad351763107ab40f1
A001846
Centered 4-dimensional orthoplex numbers (crystal ball sequence for 4-dimensional cubic lattice).
[ "1", "9", "41", "129", "321", "681", "1289", "2241", "3649", "5641", "8361", "11969", "16641", "22569", "29961", "39041", "50049", "63241", "78889", "97281", "118721", "143529", "172041", "204609", "241601", "283401", "330409", "383041", "441729", "506921", "579081", "658689", "746241", "842249", "947241", "1061761", "1186369" ]
[ "nonn", "easy" ]
111
0
5
[ "A001844", "A001845", "A001846", "A001847", "A005408", "A008288", "A008412", "A013609", "A059100", "A240876" ]
[ "M4622", "N1974" ]
N. J. A. Sloane
2024-03-23T08:19:44
oeisdata/seq/A001/A001846.seq
939ff00836132d00d9bdf480889944ff
A001847
Crystal ball sequence for 5-dimensional cubic lattice.
[ "1", "11", "61", "231", "681", "1683", "3653", "7183", "13073", "22363", "36365", "56695", "85305", "124515", "177045", "246047", "335137", "448427", "590557", "766727", "982729", "1244979", "1560549", "1937199", "2383409", "2908411", "3522221", "4235671", "5060441", "6009091", "7095093", "8332863", "9737793", "11326283" ]
[ "nonn", "easy" ]
80
0
5
[ "A001844", "A001845", "A001846", "A001847", "A005408", "A008288", "A013609", "A240876" ]
[ "M4793", "N2045" ]
N. J. A. Sloane
2024-03-23T08:19:04
oeisdata/seq/A001/A001847.seq
af2e76c8acac3cc70691c82e2dee7792
A001848
Crystal ball sequence for 6-dimensional cubic lattice.
[ "1", "13", "85", "377", "1289", "3653", "8989", "19825", "40081", "75517", "134245", "227305", "369305", "579125", "880685", "1303777", "1884961", "2668525", "3707509", "5064793", "6814249", "9041957", "11847485", "15345233", "19665841", "24957661", "31388293", "39146185", "48442297", "59511829", "72616013", "88043969" ]
[ "nonn", "easy" ]
68
0
5
[ "A001847", "A001848", "A008288", "A013609", "A240876" ]
[ "M4904", "N2102" ]
N. J. A. Sloane
2024-03-23T08:22:41
oeisdata/seq/A001/A001848.seq
3d01e9d8ee2db3194bbe0d5a3008324a
A001849
Crystal ball sequence for 7-dimensional cubic lattice.
[ "1", "15", "113", "575", "2241", "7183", "19825", "48639", "108545", "224143", "433905", "795455", "1392065", "2340495", "3800305", "5984767", "9173505", "13726991", "20103025", "28875327", "40754369", "56610575", "77500017", "104692735", "139703809", "184327311", "240673265", "311207743", "398796225", "506750351" ]
[ "nonn", "easy" ]
59
0
5
[ "A001848", "A001849", "A008288", "A240876" ]
[ "M4979", "N2139" ]
N. J. A. Sloane
2024-03-23T08:17:10
oeisdata/seq/A001/A001849.seq
a6cf108948942a1b3b8ef075ca94c8ab
A001850
Central Delannoy numbers: a(n) = Sum_{k=0..n} C(n,k)*C(n+k,k).
[ "1", "3", "13", "63", "321", "1683", "8989", "48639", "265729", "1462563", "8097453", "45046719", "251595969", "1409933619", "7923848253", "44642381823", "252055236609", "1425834724419", "8079317057869", "45849429914943", "260543813797441", "1482376214227923", "8443414161166173", "48141245001931263" ]
[ "nonn", "easy", "nice" ]
480
0
5
[ "A000129", "A001850", "A008288", "A026003", "A027618", "A047665", "A052141", "A064861", "A078057", "A084773", "A109980", "A152250", "A241023", "A243949", "A262809", "A263159" ]
[ "M2942", "N1184" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001850.seq
6e9919fcbb868dbc43ff2f6e3df4770c
A001851
Total diameter of unlabeled trees with n nodes.
[ "0", "1", "2", "5", "9", "21", "44", "103", "232", "571", "1368", "3441", "8653", "22263", "57518", "150733", "396937", "1054540", "2815453", "7562159", "20399714", "55280532", "150356806", "410432671", "1123902587", "3086827578", "8500975970", "23470712241", "64952794778", "180144093389" ]
[ "nonn" ]
28
0
5
null
[ "M1363", "N0527" ]
N. J. A. Sloane
2018-02-09T21:45:38
oeisdata/seq/A001/A001851.seq
beb201f25543aee6f0ed1dcb03cbb1fd
A001852
Total diameter of labeled trees with n nodes.
[ "0", "1", "6", "44", "430", "5322", "79184", "1381144", "27730602", "630422390", "16006336852", "448982630340", "13792542282974", "460632431511826", "16620059192605080", "644338908974954672", "26713929408696716242", "1179487563859389821166" ]
[ "nonn" ]
26
0
5
[ "A001852", "A034854" ]
[ "M4247", "N1774" ]
N. J. A. Sloane
2022-02-04T00:47:04
oeisdata/seq/A001/A001852.seq
b85718234c7ce143964906c92794de04
A001853
Total height of trees with n nodes.
[ "0", "1", "3", "8", "22", "58", "158", "425", "1161", "3175", "8751", "24192", "67239", "187459", "524579", "1472086", "4142639", "11685501", "33036492", "93583873", "265589158", "754998424", "2149588878", "6128914829", "17497927510", "50017546412", "143137957590", "410062891934", "1175925220607", "3375322972597" ]
[ "nonn" ]
27
0
5
[ "A001853", "A034781" ]
[ "M2743", "N1102" ]
N. J. A. Sloane
2022-02-04T00:46:55
oeisdata/seq/A001/A001853.seq
317121768e98eeb0136d2f6292eb24e9
A001854
Total height of all rooted trees on n labeled nodes.
[ "0", "2", "15", "148", "1785", "26106", "449701", "8927192", "200847681", "5053782070", "140679853941", "4293235236324", "142553671807729", "5116962926162738", "197459475792232725", "8152354312656732976", "358585728464893234305", "16741214317684425260142", "826842457727306803110997", "43073414675338753123113980" ]
[ "nonn" ]
47
0
5
[ "A000435", "A001854", "A034855", "A234953", "A236396" ]
[ "M2081", "N0822" ]
N. J. A. Sloane
2022-06-21T19:56:06
oeisdata/seq/A001/A001854.seq
fe15d16d112712735b6eb2007d3f7710
A001855
Sorting numbers: maximal number of comparisons for sorting n elements by binary insertion.
[ "0", "1", "3", "5", "8", "11", "14", "17", "21", "25", "29", "33", "37", "41", "45", "49", "54", "59", "64", "69", "74", "79", "84", "89", "94", "99", "104", "109", "114", "119", "124", "129", "135", "141", "147", "153", "159", "165", "171", "177", "183", "189", "195", "201", "207", "213", "219", "225", "231", "237", "243", "249", "255", "261", "267", "273", "279", "285" ]
[ "nonn", "easy", "nice" ]
124
0
5
[ "A000337", "A001855", "A003071", "A029837", "A030190", "A030308", "A061168", "A123753", "A373709" ]
[ "M2433", "N0963" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001855.seq
0c238edb4ebff673551bb6dd78e4e62b
A001856
A self-generating sequence: every positive integer occurs as a(i)-a(j) for a unique pair i,j.
[ "1", "2", "4", "8", "16", "21", "42", "51", "102", "112", "224", "235", "470", "486", "972", "990", "1980", "2002", "4004", "4027", "8054", "8078", "16156", "16181", "32362", "32389", "64778", "64806", "129612", "129641", "259282", "259313", "518626", "518658", "1037316", "1037349", "2074698", "2074734", "4149468" ]
[ "nonn", "easy", "nice" ]
49
0
5
[ "A001856", "A004978", "A054540", "A247556" ]
[ "M1112", "N0425" ]
N. J. A. Sloane
2017-06-26T22:59:36
oeisdata/seq/A001/A001856.seq
25fe88a12cabeceb044214ae7dd7766b
A001857
a(1)=2, a(2)=3; for n >= 3, a(n) is smallest number that is uniquely of the form a(j) + a(k) with 1 <= j < k < n.
[ "2", "3", "5", "7", "8", "9", "13", "14", "18", "19", "24", "25", "29", "30", "35", "36", "40", "41", "46", "51", "56", "63", "68", "72", "73", "78", "79", "83", "84", "89", "94", "115", "117", "126", "153", "160", "165", "169", "170", "175", "176", "181", "186", "191", "212", "214", "230", "235", "240", "245", "266", "273", "278", "283", "288", "325", "331", "332", "337", "342" ]
[ "nonn", "nice" ]
47
0
5
[ "A001857", "A100729", "A199122", "A199123" ]
[ "M0634", "N0231" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001857.seq
110483b282d04a287c835305b42a29fb
A001858
Number of forests of trees on n labeled nodes.
[ "1", "1", "2", "7", "38", "291", "2932", "36961", "561948", "10026505", "205608536", "4767440679", "123373203208", "3525630110107", "110284283006640", "3748357699560961", "137557910094840848", "5421179050350334929", "228359487335194570528", "10239206473040881277575", "486909744862576654283616" ]
[ "nonn", "easy", "eigen" ]
127
0
5
[ "A000055", "A000088", "A000169", "A000272", "A001858", "A002494", "A002807", "A005195", "A006125", "A006129", "A006572", "A006573", "A053530", "A054548", "A088956", "A105784", "A137916", "A138464", "A144958", "A213434", "A263340", "A322661", "A367863", "A372168", "A372176", "A372193", "A372195" ]
[ "M1804", "N0714" ]
N. J. A. Sloane and Simon Plouffe
2024-07-25T11:06:08
oeisdata/seq/A001/A001858.seq
33a9598ba023eb627d8399d19fafcb06
A001859
Triangular numbers plus quarter-squares: n*(n+1)/2 + floor((n+1)^2/4) (i.e., A000217(n) + A002620(n+1)).
[ "0", "2", "5", "10", "16", "24", "33", "44", "56", "70", "85", "102", "120", "140", "161", "184", "208", "234", "261", "290", "320", "352", "385", "420", "456", "494", "533", "574", "616", "660", "705", "752", "800", "850", "901", "954", "1008", "1064", "1121", "1180", "1240", "1302", "1365", "1430", "1496", "1564", "1633", "1704", "1776", "1850", "1925" ]
[ "nonn", "easy", "nice" ]
96
0
5
[ "A000217", "A001859", "A002378", "A002620", "A003984", "A004526", "A006578", "A045944", "A045947", "A049450", "A077043", "A107661", "A185212" ]
[ "M1368", "N0531" ]
N. J. A. Sloane
2023-08-23T07:10:37
oeisdata/seq/A001/A001859.seq
202089eeb765ebe0579a7a9892c72e57
A001860
Number of series-reduced planted trees with n+9 nodes and 4 internal nodes.
[ "0", "3", "12", "29", "57", "99", "157", "234", "333", "456", "606", "786", "998", "1245", "1530", "1855", "2223", "2637", "3099", "3612", "4179", "4802", "5484", "6228", "7036", "7911", "8856", "9873", "10965", "12135", "13385", "14718", "16137", "17644", "19242", "20934", "22722", "24609", "26598", "28691", "30891", "33201", "35623", "38160" ]
[ "nonn" ]
34
0
5
null
[ "M2917", "N1171" ]
N. J. A. Sloane
2023-06-25T02:44:31
oeisdata/seq/A001/A001860.seq
97cbf1d3ab772eed27b1a1e52723abae
A001861
Expansion of e.g.f. exp(2*(exp(x) - 1)).
[ "1", "2", "6", "22", "94", "454", "2430", "14214", "89918", "610182", "4412798", "33827974", "273646526", "2326980998", "20732504062", "192982729350", "1871953992254", "18880288847750", "197601208474238", "2142184050841734", "24016181943732414", "278028611833689478", "3319156078802044158", "40811417293301014150" ]
[ "nonn", "easy", "nice" ]
222
0
5
[ "A000110", "A000587", "A001861", "A002871", "A027710", "A033306", "A035009", "A036073", "A049020", "A056857", "A068199", "A068200", "A068201", "A078937", "A078938", "A078944", "A078945", "A109128", "A129323", "A129324", "A129325", "A129327", "A129328", "A129329", "A129331", "A129332", "A129333", "A144061", "A144180", "A144223", "A144263", "A189233", "A213170", "A221159", "A221176" ]
[ "M1662", "N0653" ]
N. J. A. Sloane, Simon Plouffe
2024-04-06T09:03:11
oeisdata/seq/A001/A001861.seq
6b5d2e949435aebab2a0305255f4025d
A001862
Number of forests of least height with n nodes.
[ "1", "1", "2", "7", "26", "111", "562", "3151", "19252", "128449", "925226", "7125009", "58399156", "507222535", "4647051970", "44747776651", "451520086208", "4761032807937", "52332895618066", "598351410294193", "7102331902602676", "87365859333294151", "1111941946738682522", "14621347433458883187" ]
[ "nonn" ]
38
0
5
[ "A000085", "A000169", "A000272", "A000666", "A001862", "A002494", "A003465", "A006125", "A006129", "A053530", "A054548", "A062740", "A066383", "A133686", "A322661", "A322700", "A368597", "A369191", "A369199" ]
[ "M1773", "N0702" ]
N. J. A. Sloane
2024-05-19T14:02:59
oeisdata/seq/A001/A001862.seq
9549acf66ee08b93ba0a07dfd99da0fb
A001863
Normalized total height of rooted trees with n nodes.
[ "0", "1", "4", "26", "236", "2760", "39572", "672592", "13227804", "295579520", "7398318500", "205075286784", "6236796259916", "206489747516416", "7393749269685300", "284714599444490240", "11733037015160276348", "515240326393584058368", "24019843795708471562564", "1184776250223810469888000" ]
[ "nonn", "nice", "easy" ]
85
0
5
[ "A000169", "A000435", "A001863", "A001864" ]
[ "M3614", "N1466" ]
N. J. A. Sloane
2023-04-26T18:33:39
oeisdata/seq/A001/A001863.seq
9fd5fd3a1e4a62b44b1969dbacd1ae67
A001864
Total height of rooted trees with n labeled nodes.
[ "0", "2", "24", "312", "4720", "82800", "1662024", "37665152", "952401888", "26602156800", "813815035000", "27069937855488", "972940216546896", "37581134047987712", "1552687346633913000", "68331503866677657600", "3191386068123595166656", "157663539876436721860608" ]
[ "nonn", "easy", "nice" ]
84
0
5
[ "A000435", "A001863", "A001864" ]
[ "M2138", "N0850" ]
N. J. A. Sloane
2023-04-26T10:09:01
oeisdata/seq/A001/A001864.seq
a02d93c110c4b33657b08332d6c836db
A001865
Number of connected functions on n labeled nodes.
[ "1", "3", "17", "142", "1569", "21576", "355081", "6805296", "148869153", "3660215680", "99920609601", "2998836525312", "98139640241473", "3478081490967552", "132705415800984825", "5423640496274200576", "236389784118231290049", "10944997108429625524224", "536484538620663729658993" ]
[ "nonn", "easy", "nice" ]
129
0
5
[ "A000435", "A001865", "A060281", "A063169" ]
[ "M3040", "N1232" ]
N. J. A. Sloane
2024-12-27T03:49:19
oeisdata/seq/A001/A001865.seq
66d18a30f11b90d95b7695b766029e3e
A001866
Number of connected graphs with n nodes and n edges.
[ "0", "0", "1", "24", "936", "56640", "4968000", "598328640", "94916183040", "19200422062080", "4826695329792000", "1476585999504000000", "540272647694971699200", "233019960215154829516800", "117009251702203840384204800", "67680314823703303654732800000", "44677678066673631080900198400000" ]
[ "nonn" ]
29
0
5
[ "A001866", "A174586" ]
[ "M5170", "N2245" ]
N. J. A. Sloane
2024-12-27T03:49:24
oeisdata/seq/A001/A001866.seq
f6c55bdddb274b4746db47422929ebd7
A001867
Number of n-bead necklaces with 3 colors.
[ "1", "3", "6", "11", "24", "51", "130", "315", "834", "2195", "5934", "16107", "44368", "122643", "341802", "956635", "2690844", "7596483", "21524542", "61171659", "174342216", "498112275", "1426419858", "4093181691", "11767920118", "33891544419", "97764131646", "282429537947", "817028472960", "2366564736723" ]
[ "nonn", "easy", "nice" ]
90
0
5
[ "A001867", "A054610", "A075195" ]
[ "M2548", "N1008" ]
N. J. A. Sloane
2025-01-05T19:51:32
oeisdata/seq/A001/A001867.seq
33615354a25d1f67a79bcc6d20dd6a6e
A001868
Number of n-bead necklaces with 4 colors.
[ "1", "4", "10", "24", "70", "208", "700", "2344", "8230", "29144", "104968", "381304", "1398500", "5162224", "19175140", "71582944", "268439590", "1010580544", "3817763740", "14467258264", "54975633976", "209430787824", "799645010860", "3059510616424", "11728124734500", "45035996273872", "173215372864600", "667199944815064" ]
[ "nonn", "nice", "easy" ]
87
0
5
[ "A001868", "A054611", "A075195" ]
[ "M3390", "N1370" ]
N. J. A. Sloane
2025-01-03T12:29:53
oeisdata/seq/A001/A001868.seq
7e2313701af113b98fa08856f3e88cdd
A001869
Number of n-bead necklaces with 5 colors.
[ "1", "5", "15", "45", "165", "629", "2635", "11165", "48915", "217045", "976887", "4438925", "20346485", "93900245", "435970995", "2034505661", "9536767665", "44878791365", "211927736135", "1003867701485", "4768372070757", "22706531350485", "108372083629275", "518301258916445" ]
[ "nonn", "easy" ]
76
0
5
[ "A001869", "A054612", "A075195" ]
[ "M3860", "N1582" ]
N. J. A. Sloane
2025-02-16T08:32:24
oeisdata/seq/A001/A001869.seq
ad496ce16730e0fbdfdef7089ef25fad
A001870
Expansion of (1-x)/(1 - 3*x + x^2)^2.
[ "1", "5", "19", "65", "210", "654", "1985", "5911", "17345", "50305", "144516", "411900", "1166209", "3283145", "9197455", "25655489", "71293590", "197452746", "545222465", "1501460635", "4124739581", "11306252545", "30928921224", "84451726200", "230204999425" ]
[ "nonn", "easy" ]
118
0
5
[ "A001870", "A001871", "A023610", "A030267", "A060921", "A121466" ]
[ "M3886", "N1595" ]
N. J. A. Sloane
2025-03-05T02:02:16
oeisdata/seq/A001/A001870.seq
a111c4958cd819e05fef5491f0bca078
A001871
Expansion of 1/(1 - 3*x + x^2)^2.
[ "1", "6", "25", "90", "300", "954", "2939", "8850", "26195", "76500", "221016", "632916", "1799125", "5082270", "14279725", "39935214", "111228804", "308681550", "853904015", "2355364650", "6480104231", "17786356776", "48715278000", "133167004200", "363372003625", "989900286774" ]
[ "nonn", "easy" ]
148
0
5
[ "A000045", "A000051", "A001629", "A001820", "A001870", "A001871", "A001906", "A002720", "A049310", "A238846" ]
[ "M4166", "N1733" ]
N. J. A. Sloane
2025-03-05T02:03:04
oeisdata/seq/A001/A001871.seq
71de5a4f48a7617b53ae1f76724e673a
A001872
Convolved Fibonacci numbers.
[ "1", "4", "14", "40", "105", "256", "594", "1324", "2860", "6020", "12402", "25088", "49963", "98160", "190570", "366108", "696787", "1315072", "2463300", "4582600", "8472280", "15574520", "28481220", "51833600", "93914325", "169457708", "304597382", "545556512", "973877245", "1733053440", "3075011478" ]
[ "nonn", "easy" ]
92
0
5
null
[ "M3476", "N1413" ]
N. J. A. Sloane, Simon Plouffe
2025-01-05T19:51:32
oeisdata/seq/A001/A001872.seq
1b5ec57cec6e587d0f508755bf429fc2
A001873
Convolved Fibonacci numbers.
[ "1", "5", "20", "65", "190", "511", "1295", "3130", "7285", "16435", "36122", "77645", "163730", "339535", "693835", "1399478", "2790100", "5504650", "10758050", "20845300", "40075630", "76495450", "145052300", "273381350", "512347975", "955187033", "1772132390", "3272875935", "6018885570", "11024814945", "20118711993" ]
[ "nonn" ]
63
0
5
null
[ "M3899", "N1600" ]
N. J. A. Sloane
2025-01-05T19:51:32
oeisdata/seq/A001/A001873.seq
bba6d50a4e5df806866e6107a351d470
A001874
Convolved Fibonacci numbers.
[ "1", "6", "27", "98", "315", "924", "2534", "6588", "16407", "39430", "91959", "209034", "464723", "1013292", "2171850", "4584620", "9546570", "19635840", "39940460", "80421600", "160437690", "317354740", "622844730", "1213580820", "2348773525", "4517541378", "8638447293", "16428864606", "31086197469", "58539877020" ]
[ "nonn", "easy" ]
52
0
5
[ "A001874", "A049310" ]
[ "M4174", "N1738" ]
N. J. A. Sloane, Simon Plouffe
2020-01-31T07:23:43
oeisdata/seq/A001/A001874.seq
b5eab6733d74c8b6398c094bdc0c0ccc
A001875
Convolved Fibonacci numbers.
[ "1", "7", "35", "140", "490", "1554", "4578", "12720", "33705", "85855", "211519", "506408", "1182650", "2702350", "6056850", "13343820", "28947240", "61926900", "130814600", "273163100", "564415390", "1154933230", "2342193350", "4710707400", "9401674275", "18629923053", "36670044621", "71728832280", "139485074370" ]
[ "nonn" ]
52
0
5
null
[ "M4412", "N1865" ]
N. J. A. Sloane, Simon Plouffe
2023-08-05T16:53:28
oeisdata/seq/A001/A001875.seq
c6c5915e78431e25d83bf69942ed67fc
A001876
Number of divisors of n of the form 5k+1; a(0)=0.
[ "0", "1", "1", "1", "1", "1", "2", "1", "1", "1", "1", "2", "2", "1", "1", "1", "2", "1", "2", "1", "1", "2", "2", "1", "2", "1", "2", "1", "1", "1", "2", "2", "2", "2", "1", "1", "3", "1", "1", "1", "1", "2", "3", "1", "2", "1", "2", "1", "3", "1", "1", "2", "2", "1", "2", "2", "2", "1", "1", "1", "2", "2", "2", "2", "2", "1", "4", "1", "1", "1", "1", "2", "3", "1", "1", "1", "2", "2", "3", "1", "2", "2", "2", "1", "3", "1", "2", "1" ]
[ "nonn", "easy" ]
38
0
5
[ "A001620", "A001876", "A001877", "A001878", "A001899", "A256779" ]
null
N. J. A. Sloane
2023-11-25T04:34:26
oeisdata/seq/A001/A001876.seq
aa0a30333036db1141bbe35555fa5e68
A001877
Number of divisors of n of the form 5k+2; a(0) = 0.
[ "0", "0", "1", "0", "1", "0", "1", "1", "1", "0", "1", "0", "2", "0", "2", "0", "1", "1", "1", "0", "1", "1", "2", "0", "2", "0", "1", "1", "2", "0", "1", "0", "2", "0", "2", "1", "2", "1", "1", "0", "1", "0", "3", "0", "2", "0", "1", "1", "2", "1", "1", "1", "2", "0", "2", "0", "2", "1", "1", "0", "2", "0", "2", "1", "2", "0", "2", "1", "2", "0", "2", "0", "3", "0", "2", "0", "1", "2", "1", "0", "1", "1", "2", "0", "4", "1", "1", "1" ]
[ "nonn", "easy" ]
29
0
5
[ "A001620", "A001876", "A001877", "A001878", "A001899", "A256780" ]
null
N. J. A. Sloane
2024-07-30T01:52:09
oeisdata/seq/A001/A001877.seq
a490fa3a1afa9f9551b73aa856a63fd7
A001878
Number of divisors of n of the form 5k+3; a(0) = 0.
[ "0", "0", "0", "1", "0", "0", "1", "0", "1", "1", "0", "0", "1", "1", "0", "1", "1", "0", "2", "0", "0", "1", "0", "1", "2", "0", "1", "1", "1", "0", "1", "0", "1", "2", "0", "0", "2", "0", "1", "2", "1", "0", "1", "1", "0", "1", "1", "0", "3", "0", "0", "1", "1", "1", "2", "0", "2", "1", "1", "0", "1", "0", "0", "2", "1", "1", "2", "0", "1", "2", "0", "0", "3", "1", "0", "1", "1", "0", "3", "0", "1", "1", "0", "1", "2", "0", "1", "1" ]
[ "nonn", "easy" ]
25
0
5
[ "A001620", "A001876", "A001877", "A001878", "A001899", "A256848" ]
null
N. J. A. Sloane
2023-11-25T04:35:23
oeisdata/seq/A001/A001878.seq
d0367df5a2b63556a772fb5d5a1795a1
A001879
a(n) = (2n+2)!/(n!*2^(n+1)).
[ "1", "6", "45", "420", "4725", "62370", "945945", "16216200", "310134825", "6547290750", "151242416325", "3794809718700", "102776096548125", "2988412653476250", "92854250304440625", "3070380543400170000", "107655217802968460625", "3989575718580595893750", "155815096120119939628125" ]
[ "nonn", "easy" ]
98
0
5
[ "A001147", "A001497", "A001814", "A001876", "A001877", "A001878", "A001879", "A002544", "A163938" ]
[ "M4251", "N1775" ]
N. J. A. Sloane
2025-03-15T05:27:57
oeisdata/seq/A001/A001879.seq
98d30a43fd8635445882d82dd95f563d
A001880
Coefficients of Bessel polynomials y_n (x).
[ "1", "15", "210", "3150", "51975", "945945", "18918900", "413513100", "9820936125", "252070693875", "6957151150950", "205552193096250", "6474894082531875", "216659917377028125", "7675951358500425000", "287080580807915895000", "11303797869311688365625", "467445288360359818884375" ]
[ "nonn", "easy" ]
36
0
5
[ "A001147", "A001497", "A001518", "A001880", "A083061", "A094665", "A160470", "A160471", "A160472" ]
[ "M4989", "N2146" ]
N. J. A. Sloane
2018-01-10T19:04:08
oeisdata/seq/A001/A001880.seq
6922c5ad2e2b1c2fec1cb159dbd5009a
A001881
Coefficients of Bessel polynomials y_n (x).
[ "1", "21", "378", "6930", "135135", "2837835", "64324260", "1571349780", "41247931725", "1159525191825", "34785755754750", "1109981842719750", "37554385678684875", "1343291487737574375", "50661278966102805000", "2009564065655411265000", "83648104232906493905625", "3646073249210806587298125" ]
[ "nonn", "easy" ]
50
0
5
[ "A001497", "A001518", "A001881", "A098503", "A130757" ]
[ "M5116", "N2217" ]
N. J. A. Sloane, Simon Plouffe
2022-09-08T08:44:29
oeisdata/seq/A001/A001881.seq
23d7f2df03af0f17fe63750809f7a4d7
A001882
a(2n) = a(2n-1) + 2a(2n-2), a(2n+1) = a(2n) + a(2n-1), with a(1) = 2 and a(2) = 3.
[ "2", "3", "5", "11", "16", "38", "54", "130", "184", "444", "628", "1516", "2144", "5176", "7320", "17672", "24992", "60336", "85328", "206000", "291328", "703328", "994656", "2401312", "3395968", "8198592", "11594560", "27991744", "39586304", "95569792", "135156096", "326295680", "461451776", "1114043136", "1575494912" ]
[ "nonn" ]
36
0
5
[ "A001882", "A161941" ]
[ "M0730", "N0273" ]
N. J. A. Sloane
2022-04-13T13:25:16
oeisdata/seq/A001/A001882.seq
03f22de4158b5672f2649981c49c0afb
A001883
Number of permutations s of {1,2,...,n} such that |s(i)-i|>1 for each i=1,2,...,n.
[ "1", "0", "0", "0", "1", "4", "29", "206", "1708", "15702", "159737", "1780696", "21599745", "283294740", "3995630216", "60312696452", "970234088153", "16571597074140", "299518677455165", "5711583170669554", "114601867572247060", "2413623459384988298", "53238503492701261201", "1227382998752177970288", "29520591675204638641249" ]
[ "nonn" ]
102
0
5
[ "A001883", "A001884", "A001891", "A075851", "A075852", "A080018", "A323671" ]
[ "M3630", "N1475" ]
N. J. A. Sloane
2022-10-30T18:19:58
oeisdata/seq/A001/A001883.seq
1c184cb17d76ae599e60dd9628d053a8
A001884
Hit polynomials.
[ "1", "0", "1", "2", "20", "104", "775", "6140", "55427", "553802", "6087992", "72994152", "948103477", "13262133736", "198769630061", "3177862894922", "53984653965996", "971068821144112", "18438722595913195", "368558842844143268", "7735520783692157215", "170095060428041137778", "3910332719957508452016", "93806427360751009531632" ]
[ "nonn" ]
26
0
5
[ "A001883", "A001884", "A001891", "A080018" ]
[ "M2117", "N0835" ]
N. J. A. Sloane
2021-12-23T22:47:54
oeisdata/seq/A001/A001884.seq
f00ca49c7227b02fa4fe432864ef7f66
A001885
Hit polynomials.
[ "2", "2", "10", "28", "207", "1288", "10366", "91296", "903037", "9832848", "117032570", "1510932116", "21028774738", "313832463386", "4999133311044", "84655108256252", "1518546437350265", "28763765236019284", "573689119174695326", "12017485839703597024", "263787711208968183879", "6054632852404055079936" ]
[ "nonn" ]
20
0
5
[ "A001883", "A001885", "A001891", "A080018" ]
[ "M0384", "N0144" ]
N. J. A. Sloane
2021-12-23T22:45:49
oeisdata/seq/A001/A001885.seq
fec9750de0e2e27a7e5d5782e5f529fd
A001886
Hit polynomials.
[ "3", "6", "44", "180", "1407", "10384", "92896", "911512", "9913152", "117788056", "1519021046", "21123287848", "315034832581", "5015656588706", "84899016219708", "1522394744470356", "28828385427350245", "574839634258405032", "12039133083940334978", "264216869431056251276", "6063573884814663905952" ]
[ "nonn" ]
24
0
5
[ "A001883", "A001886", "A001891", "A080018" ]
[ "M2604", "N1031" ]
N. J. A. Sloane
2021-12-23T22:44:05
oeisdata/seq/A001/A001886.seq
0343b0e19fa46dc74fe2cbca11071acf
A001887
Number of permutations p of {1,2,...,n} such that p(i) - i < 0 or p(i) - i > 2 for all i.
[ "1", "0", "0", "0", "1", "5", "33", "236", "1918", "17440", "175649", "1942171", "23396353", "305055960", "4280721564", "64330087888", "1030831875953", "17545848553729", "316150872317105", "6012076099604308", "120330082937778554" ]
[ "nonn" ]
55
0
5
[ "A000255", "A000271", "A001883", "A001887", "A001891", "A075851", "A075852", "A080061" ]
[ "M3970", "N1640" ]
N. J. A. Sloane
2020-01-31T15:17:57
oeisdata/seq/A001/A001887.seq
5e3072a123979152a06c2991b5511eb6
A001888
Hit polynomials.
[ "1", "1", "1", "4", "21", "122", "849", "6719", "59873", "593686", "6483027", "77309508", "999569969", "13927664613", "208044077633", "3316415176712", "56193522437465", "1008499234742158", "19110533105114433", "381290148293261075", "7989548583615385153", "175418232627066361514", "4027213499971769192903", "96489861550805864197512" ]
[ "nonn" ]
24
0
5
[ "A001883", "A001888", "A001891", "A080061" ]
[ "M3573", "N1449" ]
N. J. A. Sloane
2021-12-23T22:44:26
oeisdata/seq/A001/A001888.seq
168f0b1dcbe71832124aa8ecf2795242
A001889
Hit polynomials.
[ "1", "4", "8", "38", "209", "1400", "10849", "95516", "938441", "10179149", "120748974", "1554688240", "21588485677", "321561688748", "5113709884902", "86469576394028", "1549114961438599", "29309613834899864", "583986501706555597", "12222118836543561940", "268060239251978779839", "6148136982942476816891" ]
[ "nonn" ]
24
0
5
[ "A001883", "A001889", "A001891", "A080061" ]
[ "M3345", "N1346" ]
N. J. A. Sloane
2021-12-23T22:44:30
oeisdata/seq/A001/A001889.seq
6a8d3b243edccb98e3e09acabe8e4325
A001890
Hit polynomials.
[ "1", "10", "34", "206", "1351", "10543", "92708", "912884", "9917445", "117838808", "1519483258", "21128310078", "315093762147", "5016410089130", "84909414423784", "1522548805068310", "28830824064870329", "574880701875755325", "12039866150973004846", "264230694283295736788", "6063848537910027941323" ]
[ "nonn" ]
30
0
5
[ "A001883", "A001890", "A001891", "A080061" ]
[ "M4696", "N2005" ]
N. J. A. Sloane
2018-01-12T23:50:55
oeisdata/seq/A001/A001890.seq
4e059ecff5f8df2eeb56bde0d2020cca
A001891
Hit polynomials; convolution of natural numbers with Fibonacci numbers F(2), F(3), F(4), ....
[ "0", "1", "4", "10", "21", "40", "72", "125", "212", "354", "585", "960", "1568", "2553", "4148", "6730", "10909", "17672", "28616", "46325", "74980", "121346", "196369", "317760", "514176", "831985", "1346212", "2178250", "3524517", "5702824", "9227400", "14930285", "24157748", "39088098", "63245913", "102334080", "165580064" ]
[ "nonn", "easy", "changed" ]
96
0
5
[ "A000295", "A001883", "A001890", "A001891", "A001911", "A011794", "A080061", "A152203", "A356619", "A356620", "A356621" ]
[ "M3384", "N1365" ]
N. J. A. Sloane, Simon Plouffe
2025-04-18T17:44:57
oeisdata/seq/A001/A001891.seq
467cfeece1a0c5f35e388b8f7149451d
A001892
Number of permutations of (1,...,n) having n-2 inversions (n>=2).
[ "1", "2", "5", "15", "49", "169", "602", "2191", "8095", "30239", "113906", "431886", "1646177", "6301715", "24210652", "93299841", "360490592", "1396030396", "5417028610", "21056764914", "81978913225", "319610939055", "1247641114021", "4875896455975", "19075294462185", "74696636715792", "292758662041150" ]
[ "nonn" ]
39
0
5
[ "A001892", "A008302", "A048651" ]
[ "M1477", "N0583" ]
N. J. A. Sloane, R. K. Guy
2024-02-22T20:06:03
oeisdata/seq/A001/A001892.seq
5c4409432fd6479e95404f27a81a35aa
A001893
Number of permutations of (1,...,n) having n-3 inversions (n>=3).
[ "1", "3", "9", "29", "98", "343", "1230", "4489", "16599", "61997", "233389", "884170", "3366951", "12876702", "49424984", "190297064", "734644291", "2842707951", "11022366544", "42815701060", "166583279325", "649063995030", "2532267577126", "9891097066760", "38676401680776", "151381995733542", "593053313030007" ]
[ "nonn" ]
36
0
5
[ "A001893", "A008302", "A048651" ]
[ "M2810", "N1132" ]
N. J. A. Sloane
2017-06-29T19:23:24
oeisdata/seq/A001/A001893.seq
887556721e14152263634e5ff2557740
A001894
Number of permutations of {1,...,n} having n-4 inversions (n>=4).
[ "1", "4", "14", "49", "174", "628", "2298", "8504", "31758", "119483", "452284", "1720774", "6574987", "25214332", "96997223", "374153699", "1446677555", "5605337934", "21758936146", "84604366100", "329453055975", "1284626463105", "5015200610785", "19601107218591", "76685359017750", "300294650988857", "1176939165980809" ]
[ "nonn" ]
32
0
5
[ "A001894", "A008302", "A048651" ]
[ "M3484", "N1416" ]
N. J. A. Sloane
2017-06-29T19:23:31
oeisdata/seq/A001/A001894.seq
ad8a66a7864748bf8c78fb96c494b6ae
A001895
Number of rooted planar 2-trees with n nodes.
[ "1", "2", "4", "12", "34", "111", "360", "1226", "4206", "14728", "52024", "185824", "668676", "2424033", "8839632", "32412270", "119410390", "441819444", "1641032536", "6116579352", "22870649308", "85764947502", "322476066224", "1215486756372", "4591838372044" ]
[ "nonn", "nice", "easy" ]
28
0
5
[ "A000108", "A000207", "A001895" ]
[ "M1258", "N0481" ]
N. J. A. Sloane.
2015-08-15T07:59:06
oeisdata/seq/A001/A001895.seq
6c31ac98e7d480e101860a298e750556
A001896
Numerators of cosecant numbers -2*(2^(2*n - 1) - 1)*Bernoulli(2*n); also of Bernoulli(2*n, 1/2) and Bernoulli(2*n, 1/4).
[ "1", "-1", "7", "-31", "127", "-2555", "1414477", "-57337", "118518239", "-5749691557", "91546277357", "-1792042792463", "1982765468311237", "-286994504449393", "3187598676787461083", "-4625594554880206790555", "16555640865486520478399", "-22142170099387402072897" ]
[ "sign", "frac" ]
100
0
5
[ "A001896", "A001897", "A033469", "A036280", "A062715", "A132092", "A132099", "A145901" ]
[ "M4403", "N1858" ]
N. J. A. Sloane
2024-01-24T09:16:24
oeisdata/seq/A001/A001896.seq
3e5c36a3809fd784229c2ac22b8241e2
A001897
Denominators of cosecant numbers: -2*(2^(2*n-1)-1)*Bernoulli(2*n).
[ "1", "3", "15", "21", "15", "33", "1365", "3", "255", "399", "165", "69", "1365", "3", "435", "7161", "255", "3", "959595", "3", "6765", "903", "345", "141", "23205", "33", "795", "399", "435", "177", "28393365", "3", "255", "32361", "15", "2343", "70050435", "3", "15", "1659", "115005", "249", "1702155", "3", "30705", "136059", "705", "3", "2250885", "3", "16665", "2163" ]
[ "nonn", "frac" ]
108
0
5
[ "A001896", "A001897", "A027642", "A033469", "A132092", "A132099", "A160014", "A241171", "A277087", "A340556" ]
[ "M2983", "N1205" ]
N. J. A. Sloane
2024-01-24T09:16:14
oeisdata/seq/A001/A001897.seq
a80c262109ef08693464b465e907167a
A001898
Denominators of Bernoulli polynomials B(n)(x).
[ "1", "2", "12", "8", "240", "96", "4032", "1152", "34560", "7680", "101376", "18432", "50319360", "7741440", "6635520", "884736", "451215360", "53084160", "42361159680", "4459069440", "1471492915200", "140142182400", "1758147379200", "152882380800", "417368899584000", "33389511966720", "15410543984640" ]
[ "nonn" ]
25
0
5
[ "A001898", "A027641", "A027642", "A100615", "A100616", "A100655" ]
[ "M2014", "N0749" ]
N. J. A. Sloane
2022-07-25T04:04:49
oeisdata/seq/A001/A001898.seq
15753c037704a97a03388b1b99272b67
A001899
Number of divisors of n of the form 5k+4; a(0) = 0.
[ "0", "0", "0", "0", "1", "0", "0", "0", "1", "1", "0", "0", "1", "0", "1", "0", "1", "0", "1", "1", "1", "0", "0", "0", "2", "0", "0", "1", "2", "1", "0", "0", "1", "0", "1", "0", "2", "0", "1", "1", "1", "0", "1", "0", "2", "1", "0", "0", "2", "1", "0", "0", "1", "0", "2", "0", "2", "1", "1", "1", "1", "0", "0", "1", "2", "0", "0", "0", "2", "1", "1", "0", "3", "0", "1", "0", "2", "0", "1", "1", "1", "1", "0", "0", "3", "0", "0" ]
[ "nonn", "easy" ]
28
0
5
[ "A001620", "A001876", "A001877", "A001878", "A001899", "A256849" ]
null
N. J. A. Sloane
2023-11-25T04:34:57
oeisdata/seq/A001/A001899.seq
4f438458d2ffa667ccdcdd650e99aab7
A001900
Successive numerators of Wallis's approximation to Pi/2 (unreduced).
[ "1", "2", "4", "16", "64", "384", "2304", "18432", "147456", "1474560", "14745600", "176947200", "2123366400", "29727129600", "416179814400", "6658877030400", "106542032486400", "1917756584755200", "34519618525593600", "690392370511872000", "13807847410237440000", "303772643025223680000" ]
[ "nonn", "frac", "easy" ]
72
0
5
[ "A000246", "A001900", "A001901", "A001902", "A284230" ]
null
N. J. A. Sloane
2024-07-30T04:22:52
oeisdata/seq/A001/A001900.seq
3c91f19de59730ec0dfc904e17d438fd