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A221624
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Number of 2Xn 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, 3, 27, 410, 10055, 353654, 17052210, 1075295220, 86037489675, 8510611773950, 1020010974544958, 145633667181394028, 24424236713657975558, 4754016566455947216412, 1062903928921857001102308
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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
..2..3..1....2..3..1....2..1..3....3..1..2....2..1..3....1..3..2....1..2..3
..3..2..1....1..3..2....2..3..1....2..1..3....2..1..3....2..3..1....1..2..3
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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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