OFFSET
0,2
FORMULA
G.f.: B(x)^2 where B(x) is the g.f. of A215715.
a(n) = Sum_{k=0..n} binomial(2*n+2*k+2,k) * binomial(2*n+2*k+2,n-k)/(n+k+1).
PROG
(PARI) a(n) = sum(k=0, n, binomial(2*n+2*k+2, k)*binomial(2*n+2*k+2, n-k)/(n+k+1));
CROSSREFS
KEYWORD
nonn,new
AUTHOR
Seiichi Manyama, Dec 19 2024
STATUS
approved