OFFSET
0,2
FORMULA
a(n) = [x^n] 1/((1-x-x^3) * (1-x)^(2*n)).
a(n) ~ 3^(3*n + 5/2) / (17 * sqrt(Pi*n) * 2^(2*n)). - Vaclav Kotesovec, Apr 05 2024
MATHEMATICA
Table[Sum[Binomial[3n-2k, n-3k], {k, 0, Floor[n/3]}], {n, 0, 30}] (* Harvey P. Dale, Oct 19 2024 *)
PROG
(PARI) a(n) = sum(k=0, n\3, binomial(3*n-2*k, n-3*k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 05 2024
STATUS
approved