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A159944
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Number of different deltoids (including squares) whose vertices are on an n X n grid.
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1
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0, 1, 4, 11, 26, 46, 84, 123, 194, 268, 378, 478, 657, 800, 1019, 1239, 1548, 1793, 2197, 2505, 3003, 3434, 3991, 4444, 5223, 5801, 6582, 7292, 8274, 9006, 10199, 11034, 12330, 13398, 14744, 15912, 17705, 18906, 20586
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OFFSET
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1,3
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COMMENTS
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Only convex kites (A189417) are counted, not concave kites (A173502), distinct up to congruence.
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LINKS
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EXAMPLE
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a(1) = 0, since there is only one point on a 1 X 1 grid.
a(2) = 1, since the four points on a 2 X 2 grid build a 1 X 1 square.
a(3) = 4 since there are 3 sizes of squares on a 3 X 3 grid -- 1 X 1, 2 X 2, sqrt(2) X sqrt(2) -- and a single nonsquare deltoid.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Demacek Ondrej (demacek(AT)gjh.sk), Apr 27 2009
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EXTENSIONS
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STATUS
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approved
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