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A360001
Expansion of Product_{k>=0} (1 - x^(k^2+4)) in powers of x.
4
1, 0, 0, 0, -1, -1, 0, 0, -1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, -1, 1, -1, 0, 1, 0, -1, 0, 1, -2, 1, 0, -1, 1, 1, 0, 0, 1, -2, 0, -1, -2, 1, 0, 1, 2, 1, -1, 1, 0, -2, 1, -1, -2, 0, 1, 0, 0, 1, -1, 1, 1, 0, 0, -1, -1, 1, 1, -2, 2, 0, -2, 2, 1, -3, 0, 1, -3, 2, 2, -1, 1
OFFSET
0,30
LINKS
PROG
(PARI) my(N=100, x='x+O('x^N)); Vec(prod(k=0, sqrtint(N), 1-x^(k^2+4)))
(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=-sum(j=1, i, sumdiv(j, d, issquare(d-4)*d)*v[i-j+1])/i); v;
CROSSREFS
KEYWORD
sign,look
AUTHOR
Seiichi Manyama, Jan 21 2023
STATUS
approved