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Search: id:A120884
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| A120884 |
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(1/8)*number of lattice points with odd indices in a cubic lattice inside a sphere around the origin with radius 2*n. |
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1
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| 1, 4, 17, 35, 69, 114, 184, 272, 389, 528, 702, 901, 1166, 1442, 1791, 2157, 2584, 3058, 3596, 4194, 4878, 5590, 6388, 7232, 8219, 9228, 10339, 11512, 12776, 14138, 15600, 17172, 18865, 20621, 22493, 24420, 26559, 28768, 31109, 33512, 36117, 38781
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OFFSET
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1,2
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COMMENT
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lim n->infinity a(n)/n^3 = Pi/6.
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EXAMPLE
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a(2)=4 because the 4 lattice points in the first octant (x,y,z)={(1,1,1), (1,1,3), (1,3,1), (3,1,1)} all fulfil x^2+y^2+z^2 < (2*2)^2.
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CROSSREFS
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Cf. A000605, A117609.
Sequence in context: A063115 A009954 A031092 this_sequence A041859 A022266 A145995
Adjacent sequences: A120881 A120882 A120883 this_sequence A120885 A120886 A120887
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KEYWORD
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nonn
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AUTHOR
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Hugo Pfoertner (hugo(AT)pfoertner.org), Jul 12 2006
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