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A071339
a(n) = the maximum number of lattice points touched by an origin-centered circle with radius <= n.
9
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
0,2
FORMULA
a(n) = max(i=0 to n^2) A004018(i)
EXAMPLE
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).
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Hugo Pfoertner, May 22 2002
EXTENSIONS
Edited by Don Reble, Nov 06 2005
STATUS
approved