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Search: id:A127697
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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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+0
1
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| 0, 0, 0, 0, 0, 2, 32, 368, 3984, 64904, 947168
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OFFSET
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1,6
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COMMENT
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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), or i and i+2.
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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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Cf. A002464.
Sequence in context: A053065 A091707 A060868 this_sequence A109772 A115418 A163952
Adjacent sequences: A127694 A127695 A127696 this_sequence A127698 A127699 A127700
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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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