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 A371270 #9 Mar 17 2024 04:06:47
%S A371270 1,0,2,3,100,605,18366,238147,7688584,162016857,5839673410,
%T A371270 172051422191,7034104918380,265080848463301,12311587474831750,
%U A371270 561485310426413115,29475848282815342096,1569372890780660724401,92402629467727290784650
%N A371270 E.g.f. satisfies A(x) = 1 + x*A(x)^2 * (exp(x*A(x)^2) - 1).
%F A371270 a(n) = n! * (2*n)! * Sum_{k=0..floor(n/2)} Stirling2(n-k,k)/( (n-k)! * (2*n-k+1)! ).
%o A371270 (PARI) a(n) = n!*(2*n)!*sum(k=0, n\2, stirling(n-k, k, 2)/((n-k)!*(2*n-k+1)!));
%Y A371270 Cf. A371262, A371269, A371271.
%Y A371270 Cf. A371229.
%K A371270 nonn
%O A371270 0,3
%A A371270 _Seiichi Manyama_, Mar 16 2024