OFFSET
0,2
FORMULA
a(n) = [x^n] 1/(1 - x - x/(1 - x))^n.
a(n) ~ ((16 + 12*2^(1/3) + 9*2^(2/3))/5)^n * sqrt((1 + 2^(2/3))/(12*Pi*n)). - Vaclav Kotesovec, Nov 27 2024
PROG
(PARI) a(n) = sum(k=0, n, binomial(n+k-1, k)*binomial(2*n+k-1, n-k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 27 2024
STATUS
approved