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Search: id:A110128
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| A110128 |
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Number of permutations p of 12..n satisfying |p(i+2)-p(i)| not equal to 2 for all 0<i<n-1. |
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+0
4
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| 1, 1, 2, 4, 16, 44, 200, 1288, 9512, 78652, 744360, 7867148, 91310696, 1154292796, 15784573160, 232050062524, 3648471927912, 61080818510972, 1084657970877416, 20361216987032284, 402839381030339816, 8377409956454452732
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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When n is even: 1) Number of ways that n persons seated at a rectangular table with n/2 seats along the two opposite sides can be rearranged in such a way that neighbors are no more neighbors after the rearrangement. 2) Number of ways to arrange n kings on an n X n board, with 1 in each row and column, which are non-attacking with respect to the main four quadrants.
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REFERENCES
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Roberto Tauraso, The Dinner Table Problem: The Rectangular Case, INTEGERS, vol. 6 (2006), paper A11
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LINKS
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Roberto Tauraso, The Dinner Table Problem: The Rectangular Case
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FORMULA
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A formula is given in the Tauraso reference
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CROSSREFS
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Cf. A089222, A002464.
Adjacent sequences: A110125 A110126 A110127 this_sequence A110129 A110130 A110131
Sequence in context: A048222 A062330 A133465 this_sequence A148279 A101061 A148280
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KEYWORD
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nonn
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AUTHOR
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R. Tauraso, A. Nicolosi and G. Minenkov (tauraso(AT)mat.uniroma2.it), Jul 13 2005
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion of Vladeta Jovovic, Jan 01 2008
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