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 A380774 #9 Feb 03 2025 11:07:24
%S A380774 1,3,15,121,1493,25041,519175,12764109,365437385,11989334305,
%T A380774 443413796291,18237280179669,825743182996957,40830652259369649,
%U A380774 2189754246873652607,126605689000719768541,7850410500340268709137,519697910250629229492033,36585510030973732956134779
%N A380774 E.g.f. A(x) satisfies A(x) = exp(x / (1 + x*A(x))^2) * (1 + x*A(x))^2.
%F A380774 a(n) = n! * Sum_{k=0..n} (n-k+1)^(k-1) * binomial(2*n-4*k+2,n-k)/k!.
%o A380774 (PARI) a(n, q=1, r=1, s=0, t=-2, 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 A380774 Cf. A380765.
%K A380774 nonn
%O A380774 0,2
%A A380774 _Seiichi Manyama_, Feb 02 2025