A071339 a(n) = the maximum number of lattice points touched by an origin-centered circle with radius <= n.

1, 4, 4, 8, 8, 12, 12, 12, 12, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 36, 36, 36

Offset: 0

Author

Hugo Pfoertner, May 22 2002

Keywords

• easy
• nonn

Examples

			a(5 to 8)=12 because the circle with radius 5 touches 12 lattice points: (+-1,+-2), (+-2,+-1), (+-5,0), (0,+-5); but no circle touches more, until the radius is sqrt(65).
		

Links

• Hugo Pfoertner, FORTRAN program for A071339-A071347

Crossrefs

Cf. A004018, A071339-A071347, A071383-A071385.

Formula

a(n) = max(i=0 to n^2) A004018(i)

Extensions

Edited by Don Reble, Nov 06 2005