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A064382
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Number of ways to put numbers 1, 2, ..., n*(n+1)/2 in a triangular array of n rows in such a way that each row is increasing or decreasing.
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0
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1, 6, 240, 100800, 605404800, 65703372134400, 155590841484029952000, 9416463528385701835407360000, 16689045681854870055279680279347200000, 976264092939656812770160178186221444104192000000, 2097176933095579995533106263090939623313258344938995712000000
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 2^(n-1) * A022915(n) = 2^(n-1) * (n*(n+1)/2)!/(1!*2!*...*n!)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Sep 27 2001
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EXTENSIONS
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STATUS
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approved
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