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Search: id:A116702
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| A116702 |
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Number of permutations of length n which avoid the patterns 123, 3241. |
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+0
1
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| 1, 2, 5, 13, 32, 74, 163, 347, 722, 1480, 3005, 6065, 12196, 24470, 49031, 98167, 196454, 393044, 786241, 1572653, 3145496, 6291202, 12582635, 25165523, 50331322, 100662944, 201326213, 402652777, 805305932, 1610612270
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Also number of permutations of length n which avoid the patterns 321, 2314, 2431; or avoid the patterns 123, 2314, 2431, etc.
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LINKS
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Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.
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FORMULA
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G.f.: A(x) = -{(x^3-4x^2+3x-1)x}/{(2x-1)(x-1)^3}
Binomial transform of [1, 1, 2, 3, 3, 3, 3,...] - Gary W. Adamson (qntmpkt(AT)yahoo.com), Oct 23 2007
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CROSSREFS
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Sequence in context: A082733 A095134 A086758 this_sequence A098156 A098586 A110320
Adjacent sequences: A116699 A116700 A116701 this_sequence A116703 A116704 A116705
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KEYWORD
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nonn,easy
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AUTHOR
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Lara Pudwell (Lara.Pudwell(AT)valpo.edu), Feb 26 2006
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EXTENSIONS
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Edited by njas, Mar 16 2008
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