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Search: id:A057962
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| A057962 |
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Number of points (x,y) in square lattice with (x-1/2)^2+(y-1/2)^2 <= n. |
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+0
5
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| 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
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Always a multiple of 4. Useful for rasterizing circles.
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REFERENCES
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J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 106.
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EXAMPLE
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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).
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CROSSREFS
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Cf. A057961, A004018, A004020. Partial sums of A005883.
Sequence in context: A108269 A081523 A053006 this_sequence A073687 A090818 A075191
Adjacent sequences: A057959 A057960 A057961 this_sequence A057963 A057964 A057965
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KEYWORD
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easy,nonn
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AUTHOR
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Ken Takusagawa (kenta(AT)cs.stanford.edu), Oct 15 2000
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