OFFSET
0,3
FORMULA
a(n) = n! * Sum_{k=0..floor(n/2)} binomial(2*n-3*k,k)/(n-2*k)!.
a(n) == 1 (mod 2).
PROG
(PARI) a(n) = n!*sum(k=0, n\2, binomial(2*n-3*k, k)/(n-2*k)!);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 13 2024
STATUS
approved