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A177287
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Number of permutations of 2 copies of 1..n with all adjacent differences <= 6 in absolute value.
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0
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1, 1, 6, 90, 2520, 113400, 7484400, 681080400, 46118872800, 2475822056400, 113874710498640, 4828589411913540
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OFFSET
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0,3
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COMMENTS
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a(n) = (2n)!/2^n for n<=7.
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LINKS
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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