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A053592
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Open 3-dimensional ball numbers (version 1): a(n) is the number of integer points (i,j,k) contained in an open ball of diameter n, centered at (0,0,0).
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0
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0, 1, 1, 19, 27, 81, 93, 179, 251, 389, 485, 739, 895, 1189, 1365, 1791, 2103, 2553, 2969, 3695, 4139, 4945, 5497, 6403, 7123, 8217, 9093, 10395, 11459, 12893, 13997, 15515, 17071, 18853, 20377, 22575, 24303, 26745, 28545, 31103, 33371
(list;
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refs;
listen;
history;
text;
internal format)
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OFFSET
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0,4
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COMMENTS
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a(n)/(n/2)^3 -> (4/3)*Pi.
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LINKS
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jan 19 2000
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STATUS
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approved
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