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%I #13 Mar 12 2021 22:24:48
%S 1,-2,0,0,2,0,0,0,-1,0,0,0,-2,0,0,0,2,2,0,0,0,0,0,0,-2,-2,0,0,0,0,0,0,
%T -1,4,0,0,0,0,0,0,0,2,0,0,-2,0,0,0,-2,-2,0,0,0,0,0,0,0,4,0,0,0,0,0,0,
%U 2,0,0,0,-2,0,0,0,0,-4,0,0,4,0,0,0,0,-4,0
%N Expansion of phi(-x) * psi(-x^8) * chi(x^24) in powers of x where phi(), psi(), chi() are Ramanujan theta functions.
%C Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).
%H G. C. Greubel, <a href="/A263767/b263767.txt">Table of n, a(n) for n = 0..2500</a>
%H Michael Somos, <a href="/A010815/a010815.txt">Introduction to Ramanujan theta functions</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RamanujanThetaFunctions.html">Ramanujan Theta Functions</a>
%F Expansion of eta(q)^2 * eta(q^8) * eta(q^32) * eta(q^48)^2 / (eta(q^2) * eta(q^16) * eta(q^24) * eta(q^96)) in powers of q.
%F G.f. is a period 1 Fourier series which satisfies f(-1 / (288 t)) = 10368^(1/2) (t/i) g(t) where q = exp(2 Pi i t) and g() is the g.f. for A256574.
%F a(4*n + 2) = a(4*n + 3) = a(8*n + 5) = 0.
%e G.f. = 1 - 2*x + 2*x^4 - x^8 - 2*x^12 + 2*x^16 + 2*x^17 - 2*x^24 - 2*x^25 + ...
%t a[ n_] := SeriesCoefficient[ QPochhammer[ -x^24, x^48] EllipticTheta[ 2, Pi/4, x^4] EllipticTheta[ 4, 0, x] / (2^(1/2) x), {x, 0, n}];
%o (PARI) {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x + A)^2 * eta(x^8 + A) * eta(x^32 + A) * eta(x^48 + A)^2 / (eta(x^2 + A) * eta(x^16 + A) * eta(x^24 + A) * eta(x^96 + A)), n))};
%o (PARI) q='q+O('q^99); Vec(eta(q)^2*eta(q^8)*eta(q^32)*eta(q^48)^2/(eta(q^2)*eta(q^16)* eta(q^24)*eta(q^96))) \\ _Altug Alkan_, Jul 31 2018
%Y Cf. A256574.
%K sign
%O 0,2
%A _Michael Somos_, Oct 25 2015
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