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A015680
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Expansion of e.g.f. theta_3^(-1/2).
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3
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1, -1, 3, -15, 81, -585, 4995, -46935, 499905, -6109425, 79791075, -1138096575, 17774982225, -294439570425, 5240530570275, -100050497922375, 2002010508122625, -42495475420022625, 954152290944727875
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OFFSET
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0,3
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REFERENCES
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J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 102.
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LINKS
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FORMULA
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EXAMPLE
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theta_3(q)^(-1/2) = 1 - q + 3/2 * q^2 - 5/2 * q^3 + 27/8 *q^4 - 39/8 * q^5 + ... = 1 - q + 3/2! * q^2 - 15/3! * q^3 + 81/4! * q^4 - 585/5! * q^5 + ... .
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MATHEMATICA
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nmax = 25; CoefficientList[Series[EllipticTheta[3, 0, x]^(-1/2), {x, 0, nmax}], x] * Range[0, nmax]! (* Vaclav Kotesovec, Oct 23 2018 *)
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CROSSREFS
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Cf. A015682, A015683, A015684, A015685, A015687, A015690, A015691, A015693, A015694, A015695, A015696, A015697.
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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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