A120884 (1/8)*number of lattice points with odd indices in a cubic lattice inside a sphere around the origin with radius 2*n.

1, 4, 17, 35, 69, 114, 184, 272, 389, 528, 702, 901, 1166, 1442, 1791, 2157, 2584, 3058, 3596, 4194, 4878, 5590, 6388, 7232, 8219, 9228, 10339, 11512, 12776, 14138, 15600, 17172, 18865, 20621, 22493, 24420, 26559, 28768, 31109, 33512, 36117, 38781

Offset

1,2

Comments

lim n->infinity a(n)/n^3 = Pi/6.

Links

Table of n, a(n) for n=1..42.

Example

a(2)=4 because the 4 lattice points in the first octant (x,y,z)={(1,1,1), (1,1,3), (1,3,1), (3,1,1)} all satisfy x^2+y^2+z^2 < (2*2)^2.

Crossrefs

Cf. A000605, A117609.

Sequence in context: A063115 A009954 A031092 * A267766 A273683 A173511

Adjacent sequences: A120881 A120882 A120883 * A120885 A120886 A120887

Keyword

nonn

Author

Hugo Pfoertner, Jul 12 2006

Status

approved