id:A116842 - OEIS Search Results

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Number of permutations of length n which avoid the patterns 1234, 2143, 3421.

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1, 2, 6, 21, 69, 181, 375, 651, 1009, 1449, 1971, 2575, 3261, 4029, 4879, 5811, 6825, 7921, 9099, 10359, 11701, 13125, 14631, 16219, 17889, 19641, 21475, 23391, 25389, 27469 (list; graph; listen)

	OFFSET	`1,2`
	LINKS	`Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.`
	FORMULA	`G.f.: A(x) = -{x(18x^6+31x^5+22x^4+8x^3+3x^2-x+1)}/{(x-1)^3}` `FOr n >= 5, a(n) = 41n^2 - 339n + 739. - Franklin T. Adams-Watters, Sep 16 2006`
	CROSSREFS	`Sequence in context: A088812 A001434 A119098 this_sequence A116774 A116756 A116813` `Adjacent sequences: A116839 A116840 A116841 this_sequence A116843 A116844 A116845`
	KEYWORD	`nonn,easy`
	AUTHOR	`Lara Pudwell (Lara.Pudwell(AT)valpo.edu), Feb 26 2006`

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Last modified November 18 20:14 EST 2008. Contains 147244 sequences.

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