OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..633
FORMULA
a(n) = (1/n) * Sum_{k=0..floor(n-1)/2} 4^(n-k) * binomial(n,k) * binomial(4*n-k,n-1-2*k) for n > 0.
PROG
(PARI) a(n) = if(n==0, 1, sum(k=0, (n-1)\2, 4^(n-k)*binomial(n, k)*binomial(4*n-k, n-1-2*k))/n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 01 2024
STATUS
approved