OFFSET
0,3
REFERENCES
L. E. Dickson, Algebras and Their Arithmetics, Dover, 1960, Section 91.
LINKS
R. J. Mathar, Table of n, a(n) for n = 0..10000
FORMULA
a(n) = number of vectors of norm n in D_4 lattice (A004011) if n is a prime, otherwise a(n) = 0.
MATHEMATICA
a[p_?PrimeQ] := Reduce[ a^2 + b^2 + c^2 + d^2 == 4p, {a, b, c, d}, Integers] // Length; a[_] = 0; Table[ a[n], {n, 0, 78}] (* Jean-François Alcover, Oct 03 2012 *)
CROSSREFS
KEYWORD
nonn,easy,nice
AUTHOR
N. J. A. Sloane, Jun 09 2000
EXTENSIONS
More terms from Lambert Klasen (Lambert.Klasen(AT)gmx.net), Jun 10 2005
STATUS
approved