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 A380773 #9 Feb 03 2025 11:07:29
%S A380773 1,3,17,157,2081,36301,787435,20454393,619606321,21459697561,
%T A380773 836857705931,36298027042069,1733720198941945,90434688020581893,
%U A380773 5115766921884661099,311966602078171218481,20402441541405767271137,1424538121070974347467569,105769440064498860592940683
%N A380773 E.g.f. A(x) satisfies A(x) = exp(x / (1 + x*A(x))) * (1 + x*A(x))^2.
%F A380773 a(n) = n! * Sum_{k=0..n} (n-k+1)^(k-1) * binomial(2*n-3*k+2,n-k)/k!.
%o A380773 (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*n+((s-r)*u+t)*k+q*u, n-k)/k!);
%Y A380773 Cf. A380764.
%K A380773 nonn
%O A380773 0,2
%A A380773 _Seiichi Manyama_, Feb 02 2025