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A221622
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Number of nX7 arrays with each row a permutation of 1..7 having at least as many downsteps as the preceding row
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1
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5040, 17052210, 49096652080, 130516916069715, 332469512259607296, 827196295133181978340, 2031241364747667201263520, 4951481629224145844957738085, 12021159412525485182456506260880
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 5040*a(n-1) -8349390*a(n-2) +5234439280*a(n-3) -936232732785*a(n-4) +51206316902496*a(n-5) -99624831647040*a(n-6) +49349521382400*a(n-7)
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EXAMPLE
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Some solutions for n=3
..1..4..2..3..5..6..7....1..4..2..3..5..6..7....1..4..2..3..5..6..7
..2..1..3..7..6..4..5....2..1..3..5..4..6..7....2..1..3..6..7..5..4
..3..6..5..7..2..1..4....2..1..3..5..7..4..6....6..2..5..4..3..7..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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