OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..492
FORMULA
a(n) = Sum_{k=0..n} binomial(k+2,k) * binomial(n*k,n-k).
a(n) = [x^n] 1/(1 - x*(1+x)^n)^3.
PROG
(PARI) a(n) = sum(k=0, n, binomial(k+2, k)*binomial(n*k, n-k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 08 2023
STATUS
approved