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 A377533 #8 Oct 31 2024 13:30:42
%S A377533 1,2,6,36,264,2280,23760,283920,3830400,57728160,959212800,
%T A377533 17424348480,343508014080,7302340805760,166504724305920,
%U A377533 4053311579116800,104916366780825600,2877212787562713600,83332056329006284800,2541707625791324390400,81432631127484628992000
%N A377533 Expansion of e.g.f. 1/(1 - x * exp(x^2))^2.
%F A377533 a(n) = n! * Sum_{k=0..floor(n/2)} (n-2*k+1) * (n-2*k)^k/k!.
%F A377533 a(n) ~ n! * n * 2^(n/2) / ((1+LambertW(2))^2 * LambertW(2)^(n/2)). - _Vaclav Kotesovec_, Oct 31 2024
%o A377533 (PARI) a(n) = n!*sum(k=0, n\2, (n-2*k+1)*(n-2*k)^k/k!);
%Y A377533 Cf. A358064, A377534.
%K A377533 nonn,easy
%O A377533 0,2
%A A377533 _Seiichi Manyama_, Oct 31 2024