Lewis's odd-length alternating-pattern enumeration conjecture for 2134, 4312, 3214 and 4123

Let An(σ)A_n(\sigma) be the set of permutations of [n][n] that avoid the pattern σ\sigma and are alternating. Lewis's conjecture. For n0n\geq 0 and σ{2134,4312,3214,4123}\sigma \in \{2134,4312,3214,4123\}, we have

A2n+1(σ)=A2n+1(1234).|A_{2n+1}(\sigma)|=|A_{2n+1}(1234)|.

This predicts equal enumerations for odd-length alternating permutations avoiding each of the four specified patterns and avoiding 12341234. The statement was posed by Lewis, and the supplied text does not specify whether it has been resolved.

Sources & referencesView supporting material

Primary source

Joanna N. Chen, William Y. C. Chen and Robin D. P. Zhou, “On Pattern Avoiding Alternating Permutations”, arXiv:1212.2697 (2012).

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