Kathy Q. Ji

collaborators

4 papers

math.CO2026

Revisiting $q$ -Derangement Numbers via Decorated Permutations

Kathy Q. Ji

This paper aims to provide a direct combinatorial proof of the Gessel-Wachs formula for $q$ -derangement numbers in the setting of decorated permutations, without using the $q$ -bino…

math.CO2026

Labeled Plane Trees and Increasing Plane Trees

Lora R. Du, Kathy Q. Ji, Dax T. X. Zhang

The main aim of this paper is to establish a polynomial analogue of $(n + 1)! C_{n} = 2^{n} (2 n - 1)!!$ (with $C_{n}$ as the $n$ -th Catalan number) in the setting of labeled plane trees and incr…

math.CO2024

Signed Mahonian Polynomials on Derangements in Classical Weyl Groups

Kathy Q. Ji, Dax T. X. Zhang

The polynomial of the major index $maj_{W} (I ¨ )$ over the subset $T$ of the Coxeter group $W$ is called the Mahonian polynomial over $T$ , where $maj_{W} (I ¨ )$ is a Mahonian…

math.CO2024

New refinements of Narayana polynomials and Motzkin polynomials

Janet J. W. Dong, Lora R. Du, Kathy Q. Ji +1

Chen, Deutsch and Elizalde introduced a refinement of the Narayana polynomials by distinguishing between old (leftmost child) and young leaves of plane trees. They also provided a…

Revisiting q-Derangement Numbers via Decorated Permutations

Labeled Plane Trees and Increasing Plane Trees

Signed Mahonian Polynomials on Derangements in Classical Weyl Groups

New refinements of Narayana polynomials and Motzkin polynomials

Revisiting $q$ -Derangement Numbers via Decorated Permutations