OFFSET
0,2
FORMULA
G.f.: B(x)^2 where B(x) is the g.f. of A363311.
a(n) = 2 * Sum_{k=0..n} binomial(n,k) * binomial(3*n+2*k+2,n)/(3*n+2*k+2).
PROG
(PARI) a(n, r=2, t=3, u=2) = r*sum(k=0, n, binomial(n, k)*binomial(t*n+u*k+r, n)/(t*n+u*k+r));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 02 2024
STATUS
approved