OFFSET
0,3
FORMULA
E.g.f. satisfies A(x) = ( 1 + x*A(x) * (exp(x*A(x)) - 1) )^3.
E.g.f.: B(x)^3, where B(x) is the e.g.f. of A371272.
a(n) = 3 * n! * (3*n+2)! * Sum_{k=0..floor(n/2)} Stirling2(n-k,k)/( (n-k)! * (3*n-k+3)! ).
PROG
(PARI) a(n) = 3*n!*(3*n+2)!*sum(k=0, n\2, stirling(n-k, k, 2)/((n-k)!*(3*n-k+3)!));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 27 2024
STATUS
approved