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 A380799 #7 Feb 04 2025 08:59:53
%S A380799 1,8,130,3344,119808,5547112,316221904,21462652080,1692342355840,
%T A380799 152162079949448,15373938883590144,1725108070356807952,
%U A380799 212915967853642332160,28672289555680558679400,4184239024352928346482688,657856889310116430352244528,110868321594997440513876197376
%N A380799 Expansion of e.g.f. ( (1/x) * Series_Reversion( x * exp(-x * (1 + x)^2) / (1 + x)^3 ) )^2.
%H A380799 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A380799 E.g.f. A(x) satisfies A(x) = exp( 2 * x * A(x)^(1/2) * (1 + x*A(x)^(1/2))^2 ) * (1 + x*A(x)^(1/2))^6.
%F A380799 a(n) = 2 * n! * Sum_{k=0..n} (n+2)^(k-1) * binomial(3*n+2*k+6,n-k)/k!.
%o A380799 (PARI) a(n, q=2, r=1, s=1, t=2, u=3) = q*n!*sum(k=0, n, (r*n+(s-r)*k+q)^(k-1)*binomial(r*u*n+((s-r)*u+t)*k+q*u, n-k)/k!);
%Y A380799 Cf. A380800.
%K A380799 nonn
%O A380799 0,2
%A A380799 _Seiichi Manyama_, Feb 04 2025