login
A376792
Expansion of 1/sqrt((1 - x^4)^2 - 4*x).
1
1, 2, 6, 20, 71, 258, 954, 3572, 13501, 51404, 196858, 757472, 2926097, 11341032, 44080770, 171755976, 670664951, 2623732322, 10281616176, 40350944112, 158573538071, 623930435834, 2457658576132, 9690467310480, 38244489565051, 151064227161784, 597165099484632
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