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 A358013 #14 Oct 24 2022 14:14:15
%S A358013 1,0,0,6,12,20,750,5082,23576,453672,5755770,50894030,841270452,
%T A358013 14694142476,201442729670,3552604015170,73814245552560,
%U A358013 1369932831933392,27860865121662066,655240785723048726,15052226249248287500,357713461766745539700,9416426612423343023742
%N A358013 Expansion of e.g.f. 1/(1 - x^2 * (exp(x) - 1)).
%F A358013 a(0) = 1; a(n) = n! * Sum_{k=3..n} 1/(k-2)! * a(n-k)/(n-k)!.
%F A358013 a(n) = n! * Sum_{k=0..floor(n/3)} k! * Stirling2(n-2*k,k)/(n-2*k)!.
%o A358013 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-x^2*(exp(x)-1))))
%o A358013 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=i!*sum(j=3, i, 1/(j-2)!*v[i-j+1]/(i-j)!)); v;
%o A358013 (PARI) a(n) = n!*sum(k=0, n\3, k!*stirling(n-2*k, k, 2)/(n-2*k)!);
%Y A358013 Cf. A052848, A358014.
%Y A358013 Cf. A240989, A351503, A353998.
%K A358013 nonn
%O A358013 0,4
%A A358013 _Seiichi Manyama_, Oct 24 2022