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 A379990 #10 Jan 08 2025 19:37:32
%S A379990 1,4,25,205,2065,24601,337837,5249581,91006657,1740663937,36402220141,
%T A379990 826159146253,20220201899377,530828186303377,14878044338021677,
%U A379990 443397290411503021,14000282854007503105,466866129420834410881,16395362179348570608205,604794784980600986425645
%N A379990 Expansion of e.g.f. exp(-2*x)/(exp(-x) - x)^3.
%F A379990 a(n) = n! * Sum_{k=0..n} (k+1)^(n-k) * binomial(k+2,2)/(n-k)!.
%F A379990 a(n) ~ n! * n^2 / (2 * (LambertW(1) + 1)^3 * LambertW(1)^(n+1)). - _Vaclav Kotesovec_, Jan 08 2025
%o A379990 (PARI) a(n) = n!*sum(k=0, n, (k+1)^(n-k)*binomial(k+2, 2)/(n-k)!);
%Y A379990 Cf. A377530, A379942, A379991.
%Y A379990 Cf. A092148, A377529.
%K A379990 nonn,easy
%O A379990 0,2
%A A379990 _Seiichi Manyama_, Jan 07 2025