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 A380918 #10 Feb 08 2025 10:29:51
%S A380918 1,3,32,626,18144,701712,34047712,1990612752,136308561408,
%T A380918 10704617527040,948670854933504,93670162457937408,
%U A380918 10198210374637791232,1213835371265476399104,156812263847161339392000,21853442119644273456908288,3268006232205247017382182912,521999475213929172983534518272
%N A380918 Expansion of e.g.f. (1/x) * Series_Reversion( x * (1 - x) * exp(-2*x/(1 - x)) ).
%H A380918 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A380918 E.g.f. A(x) satisfies A(x) = exp(2*x*A(x) / (1 - x*A(x))) / (1 - x*A(x)).
%F A380918 a(n) = n! * Sum_{k=0..n} 2^k * (n+1)^(k-1) * binomial(2*n,n-k)/k!.
%o A380918 (PARI) a(n, q=2, r=2, s=2, t=1, u=1/2) = q*n!*sum(k=0, n, (r*n+(s-r)*k+q)^(k-1)*binomial((r*u+1)*n+((s-r)*u+t-1)*k+q*u-1, n-k)/k!);
%Y A380918 Cf. A380663, A380919.
%Y A380918 Cf. A380916.
%K A380918 nonn
%O A380918 0,2
%A A380918 _Seiichi Manyama_, Feb 08 2025