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 A165545 Number of permutations of length n which avoid the patterns 2341 and 3421. 4
 1, 1, 2, 6, 22, 89, 382, 1711, 7922, 37663, 182936, 904302, 4535994, 23034564, 118209806, 612165222, 3195359360, 16795435994, 88825567814, 472356139660, 2524292893556, 13549955878141, 73026827854516, 395017112175542, 2143881709415478, 11671226062503926 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS These permutations have an enumeration scheme of depth 4. G.f. is conjectured to be non-D-finite (see Albert et al link). - Jay Pantone, Oct 01 2015 LINKS Jay Pantone, Table of n, a(n) for n = 0..1000 Michael H. Albert, Cheyne Homberger, Jay Pantone, Nathaniel Shar, Vincent Vatter, Generating Permutations with Restricted Containers, arXiv:1510.00269 [math.CO], 2015. Darla Kremer and Wai Chee Shiu, Finite transition matrices for permutations avoiding pairs of length four patterns, Discrete Math. 268 (2003), 171-183. MR1983276 (2004b:05006). See Table 1. V. Vatter, Enumeration schemes for restricted permutations, Combin., Prob. and Comput. 17 (2008), 137-159. Wikipedia, Permutation classes avoiding two patterns of length 4. EXAMPLE There are 22 permutations of length 4 which avoid these two patterns, so a(4)=22. CROSSREFS Cf. A053614, A106228, A165542, A165545, A257561, A257562. Sequence in context: A165544 A150268 A369439 * A306023 A150269 A199822 Adjacent sequences: A165542 A165543 A165544 * A165546 A165547 A165548 KEYWORD nonn AUTHOR Vincent Vatter, Sep 21 2009 EXTENSIONS a(0)=1 prepended by Jay Pantone, Oct 01 2015 STATUS approved

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Last modified September 9 14:16 EDT 2024. Contains 375764 sequences. (Running on oeis4.)