OFFSET
0,2
LINKS
Winston de Greef, Table of n, a(n) for n = 0..481
FORMULA
a(n) = [x^n] 1/sqrt(1 - 4*x*(1-x)^n).
PROG
(PARI) a(n) = sum(k=0, n, (-1)^(n-k)*binomial(2*k, k)*binomial(n*k, n-k));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Mar 26 2023
STATUS
approved