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A165534
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Number of permutations of length n which avoid the patterns 1243 and 2431.
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0
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1, 2, 6, 22, 88, 363, 1507, 6241, 25721, 105485, 430767, 1752945, 7113095, 28797292, 116368938, 469531170, 1892133076, 7617145998, 30638026074, 123145086046
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OFFSET
| 1,2
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COMMENTS
| These permutations have an enumeration scheme of depth 5.
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REFERENCES
| Kremer, Darla and Shiu, Wai Chee; Finite transition matrices for permutations avoiding pairs of length four patterns. Discrete Math. 268 (2003), 171-183. MR1983276 (2004b:05006). See Table 1.
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LINKS
| V. Vatter, Enumeration schemes for restricted permutations, Combin., Prob. and Comput. 17 (2008), 137-159.
Wikipedia, Permutation classes avoiding two patterns of length 4.
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EXAMPLE
| There are 22 permutations of length 4 which avoid these two patterns, so a(4)=22.
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CROSSREFS
| Sequence in context: A101043 A101046 A150263 * A165535 A165536 A032351
Adjacent sequences: A165531 A165532 A165533 * A165535 A165536 A165537
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KEYWORD
| nonn,more,changed
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AUTHOR
| Vince Vatter (vatter(AT)gmail.com), Sep 21 2009
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