

A057962


Number of points (x,y) in square lattice with (x1/2)^2+(y1/2)^2 <= n.


4



4, 12, 16, 24, 32, 44, 52, 60, 68, 76, 80, 88, 96, 112, 120, 124, 140, 148, 156, 164, 172, 180, 188, 192, 208, 216, 232, 240, 248, 256, 268, 276, 284, 300, 308, 316, 332, 348, 360, 368, 376, 384, 392, 400, 408, 424, 432, 440, 448, 460, 468, 484, 492, 500
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OFFSET

1,1


COMMENTS

Always a multiple of 4. Useful for rasterizing circles.


REFERENCES

J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", SpringerVerlag, p. 106.


LINKS

Table of n, a(n) for n=1..54.


EXAMPLE

a(2)=12 because (1,0); (1,1); (0,1); (0,0); (0,1); (0,2); (1,1); (1,0); (1,1); (1,2); (2,0); (2,1) are covered by any disc of radius between sqrt(2.5) and sqrt(4.5) and centered at (0.5,0.5).


CROSSREFS

Cf. A057961, A004018, A004020. Partial sums of A005883.
Sequence in context: A053006 A328849 A261958 * A186303 A073687 A187084
Adjacent sequences: A057959 A057960 A057961 * A057963 A057964 A057965


KEYWORD

easy,nonn


AUTHOR

Ken Takusagawa, Oct 15 2000


STATUS

approved



