OFFSET
0,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = (4 * a(n-1) - a(n-2) - 2 * (2*n-3) * a(n-3))/3 for n > 2.
PROG
(PARI) a(n) = sum(k=0, n\3, (-1)^k*(n-k)!/(k!*(n-3*k)!));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Nov 23 2022
STATUS
approved