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Search: id:A018809
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| A018809 |
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Number of lines through exactly 2 points of an n X n grid of points. |
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+0
3
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| 0, 0, 6, 12, 48, 108, 248, 428, 764, 1196, 1900, 2668, 3824, 5244, 7248, 9380, 12192, 15372, 19528, 24020, 29732, 36052, 43808, 51836, 61636, 72492, 85308, 98492, 114012, 130668, 150196, 170828, 194768, 220276, 249452, 279284, 312572, 348036
(list; graph; listen)
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OFFSET
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0,3
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LINKS
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S. Mustonen, On lines and their intersection points in a rectangular grid of points [From Seppo Mustonen (seppo.mustonen(AT)helsinki.fi), Apr 18 2009]
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FORMULA
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(1/2) * (f(n, 3) - 2 f(n, 2) + f(n, 1)) where f(n, k) = Sum ((n - |kx|)(n - |ky|)); -n<kx<n, -n<ky<n, (x, y)=1. [From Seppo Mustonen (seppo.mustonen(AT)helsinki.fi), Apr 18 2009]
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CROSSREFS
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Sequence in context: A052904 A106692 A032470 this_sequence A117866 A094060 A076722
Adjacent sequences: A018806 A018807 A018808 this_sequence A018810 A018811 A018812
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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EXTENSIONS
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An incorrect formula removed by S. Mustonen (seppo.mustonen(AT)helsinki.fi), Apr 25 2009
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