

A175341


Number of coprime pairs (x,y) with x^2+y^2 <= n^2.


1



0, 4, 8, 16, 32, 48, 72, 88, 120, 152, 192, 224, 264, 312, 384, 440, 480, 544, 616, 672, 768, 832, 928, 1000, 1112, 1192, 1280, 1384, 1488, 1584, 1704, 1816, 1960, 2072, 2224, 2344, 2480, 2600, 2752, 2912, 3064, 3184, 3360, 3480, 3696, 3856, 4016, 4176
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OFFSET

0,2


LINKS

Table of n, a(n) for n=0..47.
Wikipedia, Gauss circle problem
J. Wu, On the primitive circle problem, Monatsh. Math. 135 (2002), 69.
W. G. Zhai, X.D. Cao, On the number of coprime integer pairs within a circle, Acta Arith. 90 (1999), 1.


FORMULA

a(n) = 4*A176562(n). [From R. J. Mathar, May 07 2010]


EXAMPLE

a(2)=8 counts (x,y)= (1,1), (1,0), (1,1), (0,1), (0,1), (1,1), (1,0) and (1,1).


CROSSREFS

Cf. A000328.
Sequence in context: A217313 A101434 A048168 * A131649 A003199 A189925
Adjacent sequences: A175338 A175339 A175340 * A175342 A175343 A175344


KEYWORD

nonn


AUTHOR

R. J. Mathar, Apr 16 2010


STATUS

approved



