OFFSET
0,3
FORMULA
a(n) = n! * Sum_{k=0..n} 3^k * (3*k-1)^(n-k) * binomial(1/3,k)/(n-k)!.
a(n) == 0 (mod 3) for n>0.
PROG
(PARI) a(n) = n!*sum(k=0, n, 3^k*(3*k-1)^(n-k)*binomial(1/3, k)/(n-k)!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jan 13 2025
STATUS
approved