A101613 (2n)! * Sum[k=n..2n, 1/k].
3, 26, 684, 35664, 3068640, 392722560, 69878833920, 16484477184000, 4976250951168000, 1870345490614272000, 856314330237628416000, 469109144339151224832000, 302956190548293037916160000
Offset: 1
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Table[ n! HarmonicNumber[ Floor[ n/2]], {n, 20}] (* Robert G. Wilson v, Dec 11 2004 *)
Table[n!Sum[1/k,{k,1,Ceiling[n/2]}],{n,20}] (* Harvey P. Dale, Apr 25 2011 *)
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 *)
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