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 A380720 #7 Jan 31 2025 09:25:07
%S A380720 1,3,27,427,9829,299421,11399767,522120299,27993612745,1721382881401,
%T A380720 119487832998811,9244561661068647,788985451618181869,
%U A380720 73644131873399817653,7463589265871298367711,816231439143125763495811,95811879190166378655829393,12015708296507465444922873585
%N A380720 E.g.f. A(x) satisfies A(x) = exp(x * A(x)^2 * (1 - x*A(x))^4) / (1 - x*A(x))^2.
%F A380720 a(n) = n! * Sum_{k=0..n} (n+k+1)^(k-1) * binomial(3*n-3*k+1,n-k)/k!.
%o A380720 (PARI) a(n) = n!*sum(k=0, n, (n+k+1)^(k-1)*binomial(3*n-3*k+1, n-k)/k!);
%Y A380720 Cf. A377742, A380674.
%K A380720 nonn
%O A380720 0,2
%A A380720 _Seiichi Manyama_, Jan 30 2025