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 A380764 #13 Feb 03 2025 11:07:48
%S A380764 1,3,21,283,5825,161281,5616415,235957275,11619036385,656499970657,
%T A380764 41874164431631,2976512157543739,233338979438666161,
%U A380764 20000563338051696609,1860931002481238778511,186799953169800497128891,20122315691834196706830017,2315417027513322899728489537
%N A380764 E.g.f. A(x) satisfies A(x) = exp(x * (1 - x*A(x))) / (1 - x*A(x))^2.
%F A380764 a(n) = n! * Sum_{k=0..n} (n-k+1)^(k-1) * binomial(3*n-4*k+1,n-k)/k!.
%o A380764 (PARI) a(n, q=1, r=1, s=0, t=-1, u=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 A380764 Cf. A377742, A380765.
%K A380764 nonn
%O A380764 0,2
%A A380764 _Seiichi Manyama_, Feb 01 2025