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

Author

Hugo Pfoertner, Jul 12 2006

Keywords

• nonn

Comments

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

Examples

			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.