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A127697
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Number of permutations of {1,2,...,n} where adjacent elements differ in value by 3 or more.
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4
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1, 1, 0, 0, 0, 0, 2, 32, 368, 3984, 44304, 521606, 6564318, 88422296, 1272704694, 19521035238, 318120059458, 5491779703870, 100150978723568, 1924351621839740, 38864316540425434
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OFFSET
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0,7
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COMMENTS
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Equivalently, number of permutations of {1,2,...,n} where elements that differ by 1 in value are neither in positions i and i+1 (adjacent), nor i and i+2.
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LINKS
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EXAMPLE
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Valid permutations of {1,...,6} are 415263 and 362514.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Richard Forster (gbrl01(AT)yahoo.co.uk), Apr 11 2007, Apr 26 2007
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EXTENSIONS
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Corrected first term to 1 (was 0).
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STATUS
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approved
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