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%I #22 Feb 18 2023 07:30:07
%S 1,288,189648,16845696,397610064,4630772160,34415914176,187485113088,
%T 814904105040,2975518758816,9486517914720,27053099888256,
%U 70486130167488,169930928938176,384163702086528
%N Duplicate of A008695.
%C Original title: Theta series of Niemeier lattice of type E_6^4.
%F This series is the q-expansion of 3/4 E_4(z)^3 + 1/4 E_6(z)^2. Cf. A004009, A013973.
%t 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 = 3/4 E4[q]^3 + 1/4 E6[q]^2 + O[q]^(3 terms); Partition[ CoefficientList[s, q], 2][[All, 1]][[1 ;; terms]] (* _Jean-François Alcover_, Jul 06 2017 *)
%Y Equal to theta series of A_11 D_7 E_6, cf. A008695
%K dead
%O 0,2
%A _N. J. A. Sloane_
%E More terms and formula in terms of Eisenstein series from _Daniel D. Briggs_, Nov 25 2011