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A268470
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Number of nX2 arrays containing 2 copies of 0..n-1 with column sums equal.
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0
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1, 4, 36, 648, 19800, 972000, 69060600, 6756825600, 866219961600, 140837901120000, 28269530815680000, 6865910948635200000
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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Some solutions for n=4
..3..1. .1..1. .2..1. .1..0. .0..0. .3..2. .0..3. .3..3. .2..2. .1..2
..1..3. .0..3. .1..3. .2..3. .2..3. .0..3. .1..0. .2..0. .3..3. .0..0
..0..0. .3..2. .3..2. .0..1. .1..2. .1..0. .3..1. .1..2. .1..1. .2..3
..2..2. .2..0. .0..0. .3..2. .3..1. .2..1. .2..2. .0..1. .0..0. .3..1
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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