%I #13 Nov 07 2023 11:11:46
%S 1,1,9,166,4719,182326,8927301,529922002,36988772211,2969132797966,
%T 269488306924833,27291375956851546,3050923148547318039,
%U 373187615576953777510,49580088565083198922845,7109665420655116517351458,1094492388113416460752513851
%N E.g.f. satisfies A(x) = 1/(2 - exp(x*A(x)^3)).
%F a(n) = (1/(3*n+1)!) * Sum_{k=0..n} (3*n+k)! * Stirling2(n,k).
%F a(n) ~ 3^(4*n) * LambertW(2*exp(1/3)/3)^(3*n + 1) * n^(n-1) / (sqrt(1 + LambertW(2*exp(1/3)/3)) * 2^(3*n + 1) * exp(n) * (3*LambertW(2*exp(1/3)/3) - 1)^(4*n + 1)). - _Vaclav Kotesovec_, Nov 07 2023
%t Table[1/(3*n+1)! * Sum[(3*n+k)! * StirlingS2[n,k], {k,0,n}], {n,0,20}] (* _Vaclav Kotesovec_, Nov 07 2023 *)
%o (PARI) a(n) = sum(k=0, n, (3*n+k)!*stirling(n, k, 2))/(3*n+1)!;
%Y Cf. A000670, A052894, A367134.
%Y Cf. A367137, A367139.
%K nonn
%O 0,3
%A _Seiichi Manyama_, Nov 06 2023