OFFSET
0,4
FORMULA
a(n) = [x^n] 1/(1 - x + n*x^3).
PROG
(PARI) a(n) = sum(k=0, n\3, (-n)^k*binomial(n-2*k, k));
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Jan 09 2024
STATUS
approved