OFFSET
0,2
FORMULA
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(n+k,k) * binomial(4*n-k+2,n-2*k).
PROG
(PARI) a(n) = sum(k=0, n\2, binomial(n+k, k)*binomial(4*n-k+2, n-2*k))/(n+1);
(PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x)^2*(1-x-x^2))/x)
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 10 2024
STATUS
approved