OFFSET
0,4
REFERENCES
J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 116.
FORMULA
G.f.: (theta_3(z)*theta_3(z)*theta_3(z)+theta_2(z)*theta_2(z)*theta_2(z))^2.
MATHEMATICA
terms = 48; t2 = EllipticTheta[2, 0, z]; t3 = EllipticTheta[3, 0, z]; s = Normal[(t3^3 + t2^3)^2 + O[z]^terms] /. z -> z^4 // Simplify[#, z > 0]&; CoefficientList[s, z][[1 ;; terms]] (* Jean-François Alcover, Jul 06 2017 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved