OFFSET
0,4
FORMULA
a(n) = Sum_{k=0..floor(n/2)} (n-2*k)^(2*k) * binomial(n-k-1,k).
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(sum(k=0, N, (x/(1-(k*x)^2))^k))
(PARI) a(n) = sum(k=0, n\2, (n-2*k)^(2*k)*binomial(n-k-1, k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 21 2023
STATUS
approved