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 A362704 #12 Feb 16 2025 08:34:05
%S A362704 1,0,1,3,18,130,1140,11886,142408,1934640,29357100,492249340,
%T A362704 9038206056,180352513848,3886286296984,89937276717120,
%U A362704 2224716791224320,58577968147130176,1635780290409117648,48286974141713673072,1502385897082471446880
%N A362704 Expansion of e.g.f. 1/(1 + LambertW(-x^2/2 * exp(x))).
%H A362704 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LambertW-Function.html">Lambert W-Function</a>.
%F A362704 a(n) = n! * Sum_{k=0..floor(n/2)} k^(n-k) / (2^k * k! * (n-2*k)!).
%o A362704 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+lambertw(-x^2/2*exp(x)))))
%Y A362704 Cf. A072034, A362705.
%Y A362704 Cf. A362350.
%K A362704 nonn,easy
%O A362704 0,4
%A A362704 _Seiichi Manyama_, Apr 30 2023