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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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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; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| 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
| Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.
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FORMULA
| 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
| Sequence in context: A095134 A086758 A179257 * A098156 A098586 A199812
Adjacent sequences: A116699 A116700 A116701 * A116703 A116704 A116705
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KEYWORD
| nonn,easy
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AUTHOR
| Lara Pudwell (Lara.Pudwell(AT)valpo.edu), Feb 26 2006
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Mar 16 2008
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