OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} 4^k * binomial(n/2+k/2-1/2,k) * binomial(n-1,n-k)/(n-k+1).
PROG
(PARI) a(n) = sum(k=0, n, 4^k*binomial(n/2+k/2-1/2, k)*binomial(n-1, n-k)/(n-k+1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 19 2024
STATUS
approved