OFFSET
1,2
FORMULA
a(n) = Sum_{k=0..n-1} binomial(n-1,k)^3 * binomial(n,k)^2.
PROG
(PARI) a(n) = sum(k=0, n-1, binomial(n-1, k)^3*binomial(n, k)^2);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 14 2024
STATUS
approved