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A008689
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Theta series of Niemeier lattice of type A_24.
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5
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1, 600, 182160, 16924320, 397150800, 4632279120, 34414027200, 187479888960, 814930462800, 2975483302200, 9486481747680, 27053266687200, 70486014432960, 169930748683920, 384163827465600
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OFFSET
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0,2
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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. 407.
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LINKS
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FORMULA
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a(n) = A023936(25n). - Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Aug 02 2001
This series is the q-expansion of 67/72 E_4(z)^3 + 5/72 E_6(z)^2. - Daniel D. Briggs, Nov 25 2011
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MATHEMATICA
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terms = 15; E4[q_] := 1 + 240 Sum[DivisorSigma[3, n]*q^(2 n), {n, 1, terms}]; E6[q_] := 1 - 504 Sum[DivisorSigma[5, n]*q^(2 n), {n, 1, terms}]; s = 67/72 E4[q]^3 + 5/72 E6[q]^2 + O[q]^(3 terms); Partition[ CoefficientList[s, q], 2][[All, 1]][[1 ;; terms]] (* Jean-François Alcover, Jul 06 2017 *)
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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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