OFFSET
0,4
FORMULA
a(n) = n! * Sum_{k=0..floor(n/2)} binomial(5*n/2-4*k-1,k)/(n-2*k)!.
a(n) == 1 (mod 15).
PROG
(PARI) a(n) = n!*sum(k=0, n\2, binomial(5*n/2-4*k-1, k)/(n-2*k)!);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 13 2024
STATUS
approved