OFFSET
0,2
FORMULA
n * a(n) = 2*(2*n-1)*a(n-1) + 4*(2*n-3)*a(n-3) - 4*(n-2)*a(n-4).
a(n) = Sum_{k=0..floor(n/2)} 2^(n-k) * binomial(n-k,k)^2.
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(1/sqrt(1-4*x-8*x^3+4*x^4))
(PARI) a(n) = sum(k=0, n\2, 2^(n-k)*binomial(n-k, k)^2);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 09 2024
STATUS
approved