Simple permutations: Decidability and unavoidable substructures
Theoretical Computer Science
Small configurations in simple permutations
European Journal of Combinatorics
Substitution-closed pattern classes
Journal of Combinatorial Theory Series A
Grid classes and partial well order
Journal of Combinatorial Theory Series A
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We prove that every sufficiently long simple permutation contains two long almost disjoint simple subsequences, and then we show how this result has enumerative consequences. For example, it implies that, for any r, the number of permutations with at most r copies of 132 has an algebraic generating function (this was previously proved, constructively, by Bóna and (independently) Mansour and Vainshtein).