5 papers
Wilf Equivalence for Length-Three Patterns and Flat POPs, and a Conjecture of Qiu and Remmel
Shiqi Cao, Sergey Kitaev, Yuxin Wu
It is well known that, for each classical pattern of length 3, the number of -avoiding permutations of length is the th Catalan number, and numerous bijections betwee…
Counting permutations avoiding two flat partially ordered patterns
Shiqi Cao, Huihua Gao, Sergey Kitaev +1
Partially ordered patterns (POPs) play an important role in the study of permutation patterns, providing a convenient framework for describing large families of classical patterns.…
On stable patterns and properties on permutations of multisets
Shaoshi Chen, Hanqian Fang, Sergey Kitaev
In this paper, we study properties and patterns on permutations of multisets whose multivariate generating functions are symmetric. We interpret this phenomenon through the lens of…
Descent generating polynomials for ()- and ()-stack-sortable (pattern-avoiding) permutations
Sergey Kitaev, Philip B. Zhang
In this paper, we find distribution of descents over - and -stack-sortable permutations in terms of Eulerian polynomials. Our results generalize the enumeration resul…
Patterns in Multi-dimensional Permutations
Shaoshi Chen, Hanqian Fang, Sergey Kitaev +1
In this paper, we propose a general framework that extends the theory of permutation patterns to higher dimensions and unifies several combinatorial objects studied in the literatu…