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A029751
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Average theta series of odd unimodular lattices in dimension 12.
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3
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1, 8, 248, 1952, 7928, 25008, 60512, 134464, 253688, 474344, 775248, 1288416, 1934432, 2970352, 4168384, 6101952, 8118008, 11358864, 14704664, 19808800, 24782928, 32809216, 39940896, 51490752, 61899872, 78150008, 92080912
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OFFSET
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0,2
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REFERENCES
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R. A. Rankin, Modular Forms, p. 240 ff.
E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, NY, 1985, p. 121.
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LINKS
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FORMULA
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G.f.: 1 + 8*Sum_{k>0} k^5 x^k/(1+(-x)^k). - Michael Somos, Sep 21 2005
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MATHEMATICA
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a[0] = 1; a[n_] := (-1)^(n-1)*8*DivisorSum[n, (-1)^(n + n/#)*#^5&]; Table[a[n], {n, 0, 26}] (* Jean-François Alcover, Jul 06 2017, translated from PARI *)
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PROG
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(PARI) a(n)=if(n<1, n==0, (-1)^(n-1)*8*sumdiv(n, d, (-1)^(n+n/d)*d^5)) /* Michael Somos, Sep 21 2005 */
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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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