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 A368273 #8 Dec 19 2023 09:16:41
%S A368273 1,-3,8,-17,20,23,-50,-1185,6648,20143,-372646,179111,25378468,
%T A368273 -126050121,-1849977930,23353880527,109161798512,-3986970251809,
%U A368273 6487865966386,680166849412311,-5885809282265124,-109572316727641433,2250978116175344846,11909910338327490623
%N A368273 Expansion of e.g.f. exp(-2*x) / (1 + x*exp(x)).
%F A368273 a(n) = n! * Sum_{k=0..n} (-1)^(n-k) * (n-k-2)^k / k!.
%o A368273 (PARI) a(n) = n!*sum(k=0, n, (-1)^(n-k)*(n-k-2)^k/k!);
%Y A368273 Cf. A302397, A368271, A368272.
%K A368273 sign
%O A368273 0,2
%A A368273 _Seiichi Manyama_, Dec 19 2023