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 A380769 #13 Feb 03 2025 11:07:40
%S A380769 1,2,15,244,6097,206806,8882599,462280960,28279981825,1989026203114,
%T A380769 158149907916031,14028441592927180,1373477000345414353,
%U A380769 147124479131269256254,17115976784139798114775,2149092237059821309705816,289673905062350873773963393,41719133895880374350508378322
%N A380769 E.g.f. A(x) satisfies A(x) = exp(x / (1 - x*A(x)^2)) / (1 - x*A(x)^2).
%F A380769 a(n) = n! * Sum_{k=0..n} (2*n-2*k+1)^(k-1) * binomial(3*n-2*k,n-k)/k!.
%o A380769 (PARI) a(n, q=1, r=2, 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 A380769 Cf. A380726, A380768.
%Y A380769 Cf. A371318, A380772.
%K A380769 nonn
%O A380769 0,2
%A A380769 _Seiichi Manyama_, Feb 02 2025