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A177292
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Number of permutations of 3 copies of 1..n with all adjacent differences <= 2 in absolute value.
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0
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1, 1, 20, 1680, 51240, 1173512, 31006978, 788946320, 18721725280, 435630242080, 9998202729808, 225310437716462
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OFFSET
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0,3
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COMMENTS
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a(n) = (3n)!/6^n for n<=3.
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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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