OFFSET
0,4
REFERENCES
J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 195.
LINKS
Andy Huchala, Table of n, a(n) for n = 0..20000
N. Heninger, E. M. Rains and N. J. A. Sloane, On the Integrality of n-th Roots of Generating Functions, arXiv:math/0509316 [math.NT], 2005-2006; J. Combinatorial Theory, Series A, 113 (2006), 1732-1745.
FORMULA
E4^7 - 1680 * E4^4 * Delta + 347760 * E4 * Delta^2 with E4(q) as in A004009 and Delta(q) as in A000594. - Andy Huchala, Jun 05 2021
EXAMPLE
G.f.: 1 + 15590400*q^3 + 36957286800*q^4 + ...
PROG
(Sage)
e4 = eisenstein_series_qexp(4, 20, normalization = "integral");
delta = CuspForms(1, 12).0.q_expansion(20);
e4^7 - 1680*e4^4*delta + 347760*e4*delta^2 # Andy Huchala, Jun 05 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved