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A165536
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Number of permutations of length n which avoid the patterns 1243 and 2341.
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0
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1, 2, 6, 22, 88, 365, 1540, 6568, 28269, 122752, 537708, 2375500, 10579400, 47469377, 214454528, 974870969, 4456401809, 20474068387, 94490731125, 437872264778
(list; graph; refs; listen; history; internal format)
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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: A150263 A165534 A165535 * A032351 A165537 A165538
Adjacent sequences: A165533 A165534 A165535 * A165537 A165538 A165539
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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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