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 A367880 #10 Dec 04 2023 06:36:03
%S A367880 1,0,4,6,104,490,7452,65534,1062224,13825746,252414020,4303920742,
%T A367880 89701635960,1870259792570,44391086228972,1085906907998670,
%U A367880 29112549152845472,813723252665063842,24402507959486170260,765358519469125339190
%N A367880 Expansion of e.g.f. 1/(1 - 2 * x * (exp(x) - 1)).
%F A367880 a(0) = 1; a(n) = 2 * n * Sum_{k=2..n} binomial(n-1,k-1) * a(n-k).
%F A367880 a(n) = n! * Sum_{k=0..floor(n/2)} 2^k * k! * Stirling2(n-k,k)/(n-k)!.
%o A367880 (PARI) a(n) = n!*sum(k=0, n\2, 2^k*k!*stirling(n-k, k, 2)/(n-k)!);
%Y A367880 Cf. A052848, A367881.
%K A367880 nonn
%O A367880 0,3
%A A367880 _Seiichi Manyama_, Dec 03 2023