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 A377688 #10 Nov 04 2024 09:08:26
%S A377688 1,0,4,6,128,850,13872,195314,3586592,74163618,1694735840,44196946882,
%T A377688 1244904944208,38788984768274,1302631536943856,47297768099973330,
%U A377688 1840951270666885952,76501162074673415746,3382517582789739956928,158445187728836733069986
%N A377688 E.g.f. satisfies A(x) = (1 + x * (exp(x*A(x)) - 1))^2.
%F A377688 E.g.f.: B(x)^2, where B(x) is the e.g.f. of A371262.
%F A377688 a(n) = 2 * n! * Sum_{k=0..floor(n/2)} (2*n-2*k+1)! * Stirling2(n-k,k)/( (n-k)! * (2*n-3*k+2)! ).
%o A377688 (PARI) a(n) = 2*n!*sum(k=0, n\2, (2*n-2*k+1)!*stirling(n-k, k, 2)/((n-k)!*(2*n-3*k+2)!));
%Y A377688 Cf. A371115, A377689.
%Y A377688 Cf. A371262.
%K A377688 nonn
%O A377688 0,3
%A A377688 _Seiichi Manyama_, Nov 04 2024