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.
%I A051685 #6 Jun 13 2013 14:50:47
%S A051685 0,0,0,-6,-30,0,420,2100,6804,-20160,-376200,-2102760,-6606600,
%T A051685 53237184,965306160,5941244400,12774059760,-305998041600,
%U A051685 -5264368533216,-33983490935520,-16008359119200,3139364813249280,52132631033313600,341037535726730304,-715693892444414400
%N A051685 Auxiliary sequence for calculation of number of even permutations of degree n and order exactly 4.
%D A051685 V. Jovovic, Some combinatorial characteristics of symmetric and alternating groups (in Russian), Belgrade, 1980, unpublished.
%F A051685 a(n) = c(n, 4), where c(n, d)=Sum_{k=1..n} (-1)^(k+1)*(n-1)!/(n-k)! *Sum_{l:lcm{k, l}=d} c(n-k, l), c(0, 1)=1.
%Y A051685 Cf. A001189, A001473, A051684.
%K A051685 easy,sign
%O A051685 1,4
%A A051685 _Vladeta Jovovic_
%E A051685 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 05 2003