OFFSET
0,2
FORMULA
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(n+1,k) * binomial(4*n-k+2,n-2*k).
PROG
(PARI) a(n) = sum(k=0, n\2, binomial(n+1, k)*binomial(4*n-k+2, n-2*k))/(n+1);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 27 2023
STATUS
approved