Stephen Linton ; James Propp ; Tom Roby ; Julian West

Equivalence Relations of Permutations Generated by Constrained Transpositions
dmtcs:2841 
Discrete Mathematics & Theoretical Computer Science,
January 1, 2010,
DMTCS Proceedings vol. AN, 22nd International Conference on Formal Power Series and Algebraic Combinatorics (FPSAC 2010)

https://doi.org/10.46298/dmtcs.2841
Equivalence Relations of Permutations Generated by Constrained TranspositionsArticle
Authors: Stephen Linton ^{1}; James Propp ^{2}; Tom Roby ^{3}; Julian West ^{4}
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Stephen Linton;James Propp;Tom Roby;Julian West
1 Centre for Interdisciplinary Research in Computational Algebra [St Andrews]
We consider a large family of equivalence relations on permutations in $S_n$ that generalise those discovered by Knuth in his study of the RobinsonSchensted correspondence. In our most general setting, two permutations are equivalent if one can be obtained from the other by a sequence of patternreplacing moves of prescribed form; however, we limit our focus to patterns where two elements are transposed, conditional upon the presence of a third element of suitable value and location. For some relations of this type, we compute the number of equivalence classes, determine how many $n$permutations are equivalent to the identity permutation, or characterise this equivalence class. Although our results include familiar integer sequences (e.g., Catalan, Fibonacci, and Tribonacci numbers) and special classes of permutations (layered, connected, and $123$avoiding), some of the sequences that arise appear to be new.