A046673
a(n) = (2n)!*Sum_{i=1..n} 1/i.
Original entry on oeis.org
2, 36, 1320, 84000, 8285760, 1173553920, 226040855040, 56865153945600, 18112111963545600, 7125892746964992000, 3394344333441245184000, 1925382105537337294848000, 1282520788685931213619200000, 991363455147400701817651200000, 880169729965718014490443776000000
Offset: 1
A101609
a(n) = n! * Sum_{k=1..floor(n/2)} 1/k.
Original entry on oeis.org
0, 2, 6, 36, 180, 1320, 9240, 84000, 756000, 8285760, 91143360, 1173553920, 15256200960, 226040855040, 3390612825600, 56865153945600, 966707617075200, 18112111963545600, 344130127307366400, 7125892746964992000
Offset: 1
A101610
n! * Sum[k=1..ceiling(n/2), 1/k].
Original entry on oeis.org
1, 2, 9, 36, 220, 1320, 10500, 84000, 828576, 8285760, 97796160, 1173553920, 16145775360, 226040855040, 3554072121600, 56865153945600, 1006228442419200, 18112111963545600, 356294637348249600
Offset: 1
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Table[n!Sum[1/k,{k,1,Ceiling[n/2]}],{n,20}] (* Harvey P. Dale, Apr 25 2011 *)
A101611
a(n) = n! * Sum_{k=ceiling(n/2)..n} 1/k.
Original entry on oeis.org
1, 3, 5, 26, 94, 684, 3828, 35664, 270576, 3068640, 29400480, 392722560, 4546558080, 69878833920, 948550176000, 16484477184000, 256697973504000, 4976250951168000, 87435019510272000, 1870345490614272000
Offset: 1
-
Rest@Table[CoefficientList[Series[(Log[1-x]-x*Log[1-x^2])/(x-1),{x, 0, 20}],x][[n]](n-1)!,{n, 1, 20}] (* Benedict W. J. Irwin, Apr 25 2017 *)
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a(n) = n! * sum(k=ceil(n/2), n, 1/k); \\ Michel Marcus, Apr 25 2017
-
import math
from sympy import factorial
def a(n): return factorial(n)*sum([1/k for k in range(int(math.ceil(n/2)), n + 1)]) # Indranil Ghosh, Apr 25 2017
A101612
n! * Sum[k=floor(n/2)..n, 1/k].
Original entry on oeis.org
3, 11, 26, 154, 684, 5508, 35664, 361296, 3068640, 37383840, 392722560, 5584394880, 69878833920, 1135360800000, 16484477184000, 301158902016000, 4976250951168000, 100951141777920000, 1870345490614272000
Offset: 2
Showing 1-5 of 5 results.