OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..floor(n/3)} 2^(n-2*k) * binomial(n,3*k) * A001764(k).
PROG
(PARI) a(n) = sum(k=0, n\3, 2^(n-2*k)*binomial(n, 3*k)*binomial(3*k, k)/(2*k+1));
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Nov 05 2023
STATUS
approved