OFFSET
0,1
REFERENCES
Ono and Skinner, Ann. Math., 147 (1998), 453-470.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane and B. K. Teo, Theta series and magic numbers for close-packed spherical clusters, J. Chem. Phys. 83 (1985) 6520-6534.
LINKS
T. D. Noe, Table of n, a(n) for n = 0..1000
G. Nebe and N. J. A. Sloane, Home page for this lattice
FORMULA
4*eta(32z)^4/eta(8z) = 4*Sum q^(x^2+2y^2+2z^2), x, y, z >= 1 and odd.
MATHEMATICA
max = 73; 4*CoefficientList[ Series[ Product[ (1-q^(4k))^4 / (1-q^k), {k, 1, max}], {q, 0, max}], q] (* Jean-François Alcover, Feb 10 2012, after A045831 *)
terms = 74; QP = QPochhammer; s = 4 QP[z^4]^4/QP[z] + O[z]^terms; CoefficientList[s, z] (* Jean-François Alcover, Jul 07 2017 *)
CROSSREFS
KEYWORD
nonn,easy,nice
AUTHOR
STATUS
approved