OFFSET
0,4
COMMENTS
a(4*n-r^2) gives number of vectors x in the lattice of norm 2n and <x,y>=r for any fixed vector in the lattice of norm 2.
REFERENCES
M. Eichler and D. Zagier, The Theory of Jacobi Forms, Birkhauser, 1985.
FORMULA
E_8*E_4, 1.
G.f.: b(z) * c(z) where b(z) is g.f. for A003783 and c(z) = 1 + 240*z^4 + 2160*z^8 + ... is A004009 expanded in powers of z^4. - Sean A. Irvine, Apr 05 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Jul 11 2000
STATUS
approved