login
A376721
Expansion of 1/sqrt((1 - x^3 - x^4)^2 - 4*x^7).
3
1, 0, 0, 1, 1, 0, 1, 4, 1, 1, 9, 9, 2, 16, 36, 17, 26, 100, 101, 61, 226, 401, 274, 477, 1227, 1289, 1225, 3186, 4982, 4432, 7841, 16040, 17902, 21457, 45517, 66610, 71327, 123444, 219825, 261945, 354095, 660573, 938598, 1138806, 1909676, 3125553
OFFSET
0,8
FORMULA
a(n) = Sum_{k=0..floor(n/3)} binomial(k,n-3*k)^2.
PROG
(PARI) my(N=50, x='x+O('x^N)); Vec(1/sqrt((1-x^3-x^4)^2-4*x^7))
(PARI) a(n) = sum(k=0, n\3, binomial(k, n-3*k)^2);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 02 2024
STATUS
approved