OFFSET
0,2
FORMULA
E.g.f.: B(x)^3, where B(x) is the e.g.f. of A380051.
a(n) = n! * Sum_{k=0..n} 3^k * k^(n-k) * binomial(k/3+1,k)/( (k/3+1)*(n-k)! ).
PROG
(PARI) a(n) = n!*sum(k=0, n, 3^k*k^(n-k)*binomial(k/3+1, k)/((k/3+1)*(n-k)!));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jan 11 2025
STATUS
approved