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 A380808 #27 Feb 05 2025 09:23:43
%S A380808 1,3,24,335,6812,183397,6168406,249350285,11785793352,638146503593,
%T A380808 38960123581154,2648475653518081,198429466488527164,
%U A380808 16246940820392924189,1443430758561178861758,138305198841617791230533,14217431594874334746229520,1560842183273111251153540945
%N A380808 Expansion of e.g.f. (1/x) * Series_Reversion( x * exp(-2*x) / (1 + x*exp(-x)) ).
%H A380808 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A380808 E.g.f. A(x) satisfies A(x) = exp(2*x*A(x)) / ( 1 - x*exp(x*A(x)) ).
%F A380808 a(n) = n! * Sum_{k=0..n} (n+k+2)^k * binomial(n,k)/(k+1)!.
%o A380808 (PARI) a(n) = n!*sum(k=0, n, (n+k+2)^k*binomial(n, k)/(k+1)!);
%Y A380808 Cf. A088690, A161633, A380826.
%Y A380808 Cf. A352448, A380828.
%K A380808 nonn
%O A380808 0,2
%A A380808 _Seiichi Manyama_, Feb 04 2025