OFFSET
0,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1752
FORMULA
a(6*n+3) = 0 for n >= 0.
MATHEMATICA
a[n_] := Sum[(-1)^k * Binomial[n, 3*k]^2, {k, 0, Floor[n/3]}]; Array[a, 30, 0] (* Amiram Eldar, May 20 2021 *)
PROG
(PARI) {a(n) = sum(k=0, n\3, (-1)^k*binomial(n, 3*k)^2)}
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Mar 27 2019
STATUS
approved