OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..floor(n/4)} binomial(2*n-7*k,k) * binomial(2*n-8*k,n-4*k).
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(1/sqrt((1-x^4)^2-4*x))
(PARI) a(n) = sum(k=0, n\4, binomial(2*n-7*k, k)*binomial(2*n-8*k, n-4*k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 04 2024
STATUS
approved