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A235455
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Number of non-equivalent (mod D_4) ways to arrange 4 points on an n X n square grid so that no three points are collinear.
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6
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1, 15, 181, 1253, 6044, 22302, 68661, 183645, 439578, 964938, 1974128, 3801457, 6966581
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OFFSET
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2,2
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COMMENTS
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Also number of non-equivalent complete quadrangles on an n X n grid.
Without the restriction "non-equivalent (mod D_4)" the numbers are given by A175383, n >= 2.
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LINKS
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EXAMPLE
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There are a(3) = 15 non-equivalent ways to place 4 points (X) on a 3 X 3 grid. Examples are:
X . X . X . X X .
. . . X . X X . .
X . X . X . . . X
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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