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 A380915 #9 Feb 08 2025 10:30:02
%S A380915 1,2,19,421,14453,676741,40225525,2901397997,246222420841,
%T A380915 24038780973913,2654362957336481,327087730518759937,
%U A380915 44498835149618922253,6624743172003104909957,1071295799491745519081629,186999332904147675923216341,35044146207707289182759039825
%N A380915 E.g.f. A(x) satisfies A(x) = exp(x / (1 - x*A(x)^3)) / (1 - x*A(x)^3).
%F A380915 a(n) = n! * Sum_{k=0..n} (3*n-3*k+1)^(k-1) * binomial(4*n-3*k,n-k)/k!.
%o A380915 (PARI) a(n, q=1, r=3, s=0, t=1, u=1) = 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 A380915 Cf. A380769, A380914.
%Y A380915 Cf. A380727.
%K A380915 nonn
%O A380915 0,2
%A A380915 _Seiichi Manyama_, Feb 08 2025