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A320139
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Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 4*d^2 = n.
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18
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1, 2, 2, 6, 8, 8, 16, 16, 14, 22, 24, 16, 22, 32, 12, 32, 44, 16, 42, 52, 36, 40, 64, 32, 40, 86, 24, 50, 72, 40, 60, 80, 38, 48, 112, 48, 72, 96, 64, 80, 120, 64, 48, 124, 52, 104, 96, 64, 106, 110, 110, 96, 144, 72, 128, 160, 60, 132, 120, 64, 144, 160, 60, 112, 164
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OFFSET
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0,2
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COMMENTS
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a(n) > 0 for n >= 0.
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LINKS
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FORMULA
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G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3) * theta_3(q^4).
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MATHEMATICA
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CoefficientList[Series[Product[EllipticTheta[3, 0, q^k], {k, 1, 4}], {q, 0, 70}], q] (* G. C. Greubel, Oct 29 2018 *)
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PROG
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(PARI) q='q+O('q^70); Vec(prod(k=1, 4, eta(q^(2*k))^5/(eta(q^k)* eta(q^(4*k)))^2 )) \\ G. C. Greubel, Oct 29 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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