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 A358064 #20 Feb 14 2024 15:39:36
%S A358064 1,1,2,12,72,540,5040,53760,658560,9087120,139104000,2343781440,
%T A358064 43078210560,857676980160,18390744852480,422504399116800,
%U A358064 10353592759910400,269576216304595200,7431814422621388800,216266552026593868800,6624610236968435712000
%N A358064 Expansion of e.g.f. 1/(1 - x * exp(x^2)).
%H A358064 Seiichi Manyama, <a href="/A358064/b358064.txt">Table of n, a(n) for n = 0..420</a>
%F A358064 a(n) = n! * Sum_{k=0..floor(n/2)} (n - 2*k)^k/k!.
%F A358064 a(n) ~ n! * 2^(n/2) / ((1 + LambertW(2)) * LambertW(2)^(n/2)). - _Vaclav Kotesovec_, Nov 01 2022
%t A358064 With[{nn=30},CoefficientList[Series[1/(1-x Exp[x^2]),{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Feb 14 2024 *)
%o A358064 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-x*exp(x^2))))
%o A358064 (PARI) a(n) = n!*sum(k=0, n\2, (n-2*k)^k/k!);
%Y A358064 Cf. A216688, A358065.
%K A358064 nonn,easy
%O A358064 0,3
%A A358064 _Seiichi Manyama_, Oct 29 2022