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 A368236 #14 Dec 29 2023 06:02:00
%S A368236 1,3,17,145,1649,23441,399865,7957881,180997857,4631289697,
%T A368236 131670338921,4117813225769,140486274499345,5192341564319313,
%U A368236 206669931188282073,8813624820931402201,400922608851086766017,19377398675442025382081,991639882680576890150089
%N A368236 Expansion of e.g.f. 1/(exp(-x) - 2*x).
%F A368236 a(0) = 1; a(n) = 2*n*a(n-1) + Sum_{k=1..n} (-1)^(k-1) * binomial(n,k) * a(n-k).
%F A368236 a(n) = n! * Sum_{k=0..n} 2^(n-k) * (n-k+1)^k / k!.
%F A368236 a(n) ~ n! / (2 * LambertW(1/2)^(n+1) * (LambertW(1/2) + 1)). - _Vaclav Kotesovec_, Dec 29 2023
%o A368236 (PARI) a(n) = n!*sum(k=0, n, 2^(n-k)*(n-k+1)^k/k!);
%Y A368236 Cf. A072597, A368237.
%Y A368236 Cf. A336947, A368233.
%K A368236 nonn
%O A368236 0,2
%A A368236 _Seiichi Manyama_, Dec 18 2023