Pattern-restricted permutations composed of 3-cycles |
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Affiliation: | University of Texas at Tyler, Tyler, TX 75799, USA |
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Abstract: | In this paper, we characterize and enumerate pattern-avoiding permutations composed of only 3-cycles. In particular, we answer the question for the six patterns of length 3. We find that the number of permutations composed of n 3-cycles that avoid the pattern 231 (equivalently 312) is given by , while the generating function for the number of those that avoid the pattern 132 (equivalently 213) is given by a formula involving the generating functions for the well-known Motzkin numbers and Catalan numbers. The number of permutations composed of n 3-cycles that avoid the pattern 321 is characterized by a weighted sum involving statistics on Dyck paths of semilength n. |
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Keywords: | Pattern avoidance Cycles Dyck paths Motzkin numbers Catalan numbers |
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