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 A380722 #9 Jan 31 2025 09:25:30
%S A380722 1,3,33,679,20905,863601,44912347,2820755183,207815625073,
%T A380722 17578781394913,1679410405425571,178871724214036767,
%U A380722 21017369600310686665,2700840226820242034321,376826763817725194699083,56730569139675562422229711,9166624006966363722766482913,1582356756863532248954506939329
%N A380722 E.g.f. A(x) satisfies A(x) = exp(x * A(x)^2 * (1 - x*A(x))) / (1 - x*A(x))^2.
%F A380722 a(n) = n! * Sum_{k=0..n} (n+k+1)^(k-1) * binomial(3*n+1,n-k)/k!.
%o A380722 (PARI) a(n) = n!*sum(k=0, n, (n+k+1)^(k-1)*binomial(3*n+1, n-k)/k!);
%Y A380722 Cf. A380665, A380721.
%K A380722 nonn
%O A380722 0,2
%A A380722 _Seiichi Manyama_, Jan 30 2025