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A320540
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(1/4) * number of ways to select 3 distinct collinear points from a square of grid points with side length n.
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6
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0, 2, 11, 38, 93, 206, 386, 678, 1112, 1748, 2583, 3768, 5253, 7172, 9630, 12720, 16370, 20910, 26169, 32566, 40139, 48962, 58900, 70710, 84096, 99284, 116469, 136116, 157671, 182436, 209436, 239596, 272976, 309630, 350035, 395346, 444021, 496890, 554402, 617906
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OFFSET
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1,2
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COMMENTS
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Permutations of the 3 points are not counted separately.
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LINKS
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EXAMPLE
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a(2) = 2 because there are 8 triples of collinear points in the square [0 2] X [0 2]: The 2*3 lines of x=0,1,2 and y=0,1,2 and the 2 diagonals.
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CROSSREFS
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(1/2)* diagonal of triangle A320539.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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