OFFSET
0,2
REFERENCES
J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 407.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
This series is the q-expansion of (47*E_4(z)^3 + 25*E_6(z)^2)/72. - Daniel D. Briggs, Nov 25 2011
MATHEMATICA
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 = 47/72 E4[q]^3 + 25/72 E6[q]^2 + O[q]^(3 terms); Partition[ CoefficientList[s, q], 2][[All, 1]][[1 ;; terms]] (* Jean-François Alcover, Jul 06 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved