OFFSET
0,2
FORMULA
a(n) = 4 * Sum_{k=0..n} (-1)^(n-k) * binomial(n-1,n-k) * binomial(3*k+4,k)/(3*k+4).
PROG
(PARI) a(n) = 4*sum(k=0, n, (-1)^(n-k)*binomial(n-1, n-k)*binomial(3*k+4, k)/(3*k+4));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 27 2024
STATUS
approved