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 A377720 #10 Nov 05 2024 08:11:45
%S A377720 1,0,6,9,300,1455,44658,430941,13821048,213210171,7400153550,
%T A377720 160981385433,6126989357844,173482562393751,7273217782923498,
%U A377720 253885773923800245,11726322434886352368,485729504795911017075,24658741688798553168582,1179026561203600147075857
%N A377720 E.g.f. satisfies A(x) = (1 + x * (exp(x) - 1) * A(x))^3.
%F A377720 E.g.f.: B(x)^3, where B(x) is the e.g.f. of A371143.
%F A377720 a(n) = 3 * n! * Sum_{k=0..floor(n/2)} (3*k+2)! * Stirling2(n-k,k)/( (n-k)! * (2*k+3)! ).
%o A377720 (PARI) a(n) = 3*n!*sum(k=0, n\2, (3*k+2)!*stirling(n-k, k, 2)/((n-k)!*(2*k+3)!));
%Y A377720 Cf. A371143, A377691.
%K A377720 nonn
%O A377720 0,3
%A A377720 _Seiichi Manyama_, Nov 04 2024