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A221625
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Number of 3Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row
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1
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1, 4, 112, 6120, 738150, 148700748, 49096652080, 24099422236160, 17023170538890750, 16517958827528755300, 21433818529290626472948, 36180795747764068402865136, 77856103174007703918070147632
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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=3
..3..1..2....1..2..3....1..3..2....1..2..3....1..2..3....2..3..1....2..3..1
..1..3..2....3..1..2....3..1..2....1..2..3....2..1..3....2..3..1....1..3..2
..1..3..2....2..3..1....3..2..1....1..2..3....3..2..1....2..1..3....3..1..2
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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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