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 A368271 #11 Dec 19 2023 09:16:52
%S A368271 1,1,0,-1,4,7,-74,23,2136,-7345,-77006,712879,2499124,-69799897,
%T A368271 88342398,7311735143,-50617554896,-762825930977,12821702643946,
%U A368271 56041362405119,-2956159258069044,8447845572175031,660257137187089270,-7376306690095890185
%N A368271 Expansion of e.g.f. exp(2*x) / (1 + x*exp(x)).
%F A368271 a(n) = n! * Sum_{k=0..n} (-1)^(n-k) * (n-k+2)^k / k!.
%o A368271 (PARI) a(n) = n!*sum(k=0, n, (-1)^(n-k)*(n-k+2)^k/k!);
%Y A368271 Cf. A302397, A368272, A368273.
%Y A368271 Cf. A368265, A368267.
%K A368271 sign,easy
%O A368271 0,5
%A A368271 _Seiichi Manyama_, Dec 19 2023