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A279362
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Expansion of psi(x)^2 * chi(-x^5) in powers of x where psi(), chi() are Ramanujan theta functions.
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1
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1, 2, 1, 2, 2, -1, 1, 1, -2, 0, 2, -1, -1, 2, -2, -1, 0, -2, -2, -2, 0, -1, 1, 0, 2, -2, -5, 0, -2, 0, 0, 1, -2, 0, 0, -3, -1, 0, 0, -2, 1, -1, 2, 2, 0, 0, 0, -2, -2, 0, 2, 2, -2, 0, -2, 2, 1, 1, 0, 0, 0, -1, 2, 0, 4, 0, 1, 2, 0, 2, -1, 0, 0, 2, -2, -2, 4, -1
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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Expansion of q^(-1/24) * eta(q^2)^4 * eta(q^5) / (eta(q)^2 * eta(q^10)) in powers of q.
Euler transform of period 10 sequence [ 2, -2, 2, -2, 1, -2, 2, -2, 2, -2, ...].
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EXAMPLE
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G.f. = 1 + 2*x + x^2 + 2*x^3 + 2*x^4 - x^5 + x^6 + x^7 - 2*x^8 + 2*x^10 + ...
G.f. = q + 2*q^25 + q^49 + 2*q^73 + 2*q^97 - q^121 + q^145 + q^169 - ...
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MATHEMATICA
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a[ n_] := SeriesCoefficient[ x^(-1/4) / 4 EllipticTheta[ 2, 0, x^(1/2)]^2 QPochhammer[ x^5, x^10], {x, 0, n}];
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PROG
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(PARI) {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^2 + A)^4 * eta(x^5 + A) / (eta(x + A)^2 * eta(x^10 + A)), n))};
(PARI) lista(nn) = {q='q+O('q^nn); Vec(eta(q^2)^4*eta(q^5)/(eta(q)^2*eta(q^10)))} \\ Altug Alkan, Mar 21 2018
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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