OFFSET
0,6
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = (2 * a(n-1) - n * a(n-3) + 1)/3 for n > 2.
PROG
(PARI) a(n) = sum(k=0, n\3, (-1)^k*(n-2*k)!/(n-3*k)!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Nov 23 2022
STATUS
approved