OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * binomial(n+2*k-1,n-k) / (n-k+1).
PROG
(PARI) a(n) = sum(k=0, n, (-1)^(n-k)*binomial(n, k)*binomial(n+2*k-1, n-k)/(n-k+1));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Aug 21 2023
STATUS
approved