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Search: id:A078628
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| A078628 |
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Number of ways of arranging the numbers 1..n in a circle so that there is no consecutive triple i, i+1, i+2 or i, i-1, i-2 (mod n). |
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+0
3
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| 1, 1, 0, 4, 12, 76, 494, 3662, 30574, 284398, 2918924, 32791604, 400400062
(list; graph; listen)
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OFFSET
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1,4
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LINKS
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N. J. A. Sloane, FORTRAN program
Index entries for sequences related to shoe lacings
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EXAMPLE
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a(4) = 4: 4 2 1 3, 4 3 1 2, 4 1 3 2, 4 2 3 1.
a(5) = 12: 5 3 1 2 4, 5 2 3 1 4, 5 4 2 1 3, 5 2 4 1 3, 5 1 4 2 3, 5 2 1 4 3, 5 1 3 4 2, 5 3 1 4 2, 5 4 1 3 2, 5 3 4 1 2, 5 2 4 3 1, 5 3 2 4 1.
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CROSSREFS
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Cf. A078673. See A002816, A078603 for analogous sequence with restrictions only on pairs.
Sequence in context: A013195 A052558 A133666 this_sequence A027145 A010370 A081214
Adjacent sequences: A078625 A078626 A078627 this_sequence A078629 A078630 A078631
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KEYWORD
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nonn
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AUTHOR
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njas, Dec 12 2002
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EXTENSIONS
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a(11)-a(13) from John W. Layman (layman(AT)math.vt.edu), Nov 15 2004
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