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 A377531 #9 Oct 31 2024 13:28:16
%S A377531 1,0,4,12,96,760,7260,80724,1008112,14079888,216881460,3652767580,
%T A377531 66773963784,1316433381432,27840054610732,628626642921060,
%U A377531 15093709672205280,383989133237230624,10317497504580922212,291958800400148127660,8678485827979443326200
%N A377531 Expansion of e.g.f. 1/(1 - x^2 * exp(x))^2.
%F A377531 a(n) = n! * Sum_{k=0..floor(n/2)} (k+1) * k^(n-2*k)/(n-2*k)!.
%F A377531 a(n) ~ n! * n / ((1 + LambertW(1/2))^2 * 2^(n+2) * LambertW(1/2)^n). - _Vaclav Kotesovec_, Oct 31 2024
%o A377531 (PARI) a(n) = n!*sum(k=0, n\2, (k+1)*k^(n-2*k)/(n-2*k)!);
%Y A377531 Cf. A358080, A377532.
%K A377531 nonn,easy
%O A377531 0,3
%A A377531 _Seiichi Manyama_, Oct 31 2024