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Search: id:A047809
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| A047809 |
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a(n) counts different values of i^2+j^2+k^2 <= n^2 or number of distances from the origin to all integer points inside a sphere of radius n. |
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+0
2
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| 1, 2, 5, 9, 15, 23, 32, 43, 55, 70, 86, 103, 122, 143, 166, 190, 215, 243, 273, 304, 336, 371, 406, 443, 482, 523, 566, 611, 656, 704, 753, 803, 855, 910, 966, 1024, 1083, 1145, 1207, 1270, 1336, 1404, 1474, 1544, 1616, 1690, 1766, 1843, 1922, 2004
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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T. D. Noe, Table of n, a(n) for n = 0..1000
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FORMULA
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a(n) = number of b(i) <= n^2, b() = A000378.
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MATHEMATICA
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Table[ Length@Union@Flatten@Table[ i^2+j^2+k^2, {i, 0, n}, {j, 0, Min[ i, Floor[ Sqrt[ n^2-i^2 ] ] ]}, {k, 0, Min[ j, Floor[ Sqrt[ n^2-i^2-j^2 ] ] ]} ], {n, 0, 64} ]
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CROSSREFS
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Cf. A047808, A000378.
Sequence in context: A022941 A007982 A011904 this_sequence A014126 A019450 A098169
Adjacent sequences: A047806 A047807 A047808 this_sequence A047810 A047811 A047812
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KEYWORD
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nonn,easy,nice
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AUTHOR
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W. Meeussen (wouter.meeussen(AT)pandora.be),David W. Wilson (davidwwilson(AT)comcast.net)
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