OFFSET
0,4
FORMULA
a(n) = [x^n] 1/(1 - x*(1-x)^n).
PROG
(PARI) a(n) = sum(k=0, n, (-1)^(n-k)*binomial(n*k, n-k));
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Mar 26 2023
STATUS
approved