OFFSET
0,2
REFERENCES
J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 123.
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..422
FORMULA
a(n) ~ (-1)^n * c * exp(Pi*sqrt(3)*n), where c = 512 * Pi^12 / (9 * Gamma(1/3)^18) = 1.0411095643149212575756525710182812978684243780094495837147096816494... - Vaclav Kotesovec, Jul 02 2017, updated Mar 05 2018
MATHEMATICA
terms = 12; s = 1/(1 + 240*Sum[k^3*(q^k/(1 - q^k)), {k, 1, terms}]) + O[q]^terms; CoefficientList[s, q] (* Jean-François Alcover, Jul 04 2017 *)
CROSSREFS
KEYWORD
sign
AUTHOR
STATUS
approved