OFFSET
0,2
FORMULA
G.f. satisfies A(x) = ( 1 + x * A(x)^2 * (1 + A(x)^(1/2)) )^2.
a(n) = 2 * Sum_{k=0..n} binomial(n,k) * binomial(4*n+k+2,n)/(4*n+k+2).
PROG
(PARI) a(n, r=2, t=4, u=1) = 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