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Search: id:A117156
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| A117156 |
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Number of permutations avoiding the pattern 1342. |
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+0
1
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| 1, 1, 2, 6, 23, 110, 630, 4210, 32150, 276210, 2636720, 27687440, 317169270, 3936056080, 52603684760, 753241509900, 11504852242400, 186705357825800, 3208160592252000, 58188413286031600, 1110946958902609400
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OFFSET
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0,3
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COMMENT
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a(n) is the number of permutations on [n] that avoid the consecutive pattern 1342. It is the same as the number of permutations which avoid 2431, 4213, 3124, 1432, 2341, 4123 or 3214.
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REFERENCES
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Sergi Elizalde, Asymptotic enumeration of permutations avoiding generalized patterns, Adv. Appl. Math. 36 (2006) 138-155.
Sergi Elizalde and Marc Noy, Consecutive patterns in permutations, Adv. Appl. Math. 30 (2003) 110-125.
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MATHEMATICA
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a[n_]:=Coefficient[Series[1/(1-Integrate[Exp[ -t^3/6], {t, 0, x}]), {x, 0, 30}], x^n]*n!
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CROSSREFS
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Cf. A049774, A111004, A113228, A113229.
Sequence in context: A093345 A002136 A117226 this_sequence A113229 A113228 A063255
Adjacent sequences: A117153 A117154 A117155 this_sequence A117157 A117158 A117159
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KEYWORD
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nonn
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AUTHOR
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S. R. Finch (Steven.Finch(AT)inria.fr), Apr 26 2006
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