axioms Article Hankel Transform of the Type 2 ( p, q)-Analogue of r -Dowling Numbers Roberto Corcino 1, * ,† , Mary Ann Ritzell Vega 2,† and Amerah Dibagulun 3,†   Citation: Corcino, R.; Vega, M.A.R.; Dibagulun, A. Hankel Transform of the Type 2 ( p, q)-Analogue of r-Dowling Numbers. Axioms 2021, 10, 343. https://doi.org/10.3390/ axioms10040343 Academic Editor: Stevan Pilipovi´ c Received: 19 October 2021 Accepted: 9 December 2021 Published: 16 December 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Research Institute for Computational Mathematics and Physics, Cebu Normal University, Cebu City 6000, Philippines 2 Department of Mathematics and Statistics, Mindanao State University-Iligan Institute of Technology, Iligan City 9200, Philippines; maryannritzell.vega@g.msuiit.edu.ph 3 Department of Mathematics, Mindanao State University-Main Campus, Marawi City 9700, Philippines; a.dibagulun@yahoo.com * Correspondence: rcorcino@yahoo.com These authors contributed equally to this work. Abstract: In this paper, type 2 ( p, q)-analogues of the r-Whitney numbers of the second kind is defined and a combinatorial interpretation in the context of the A-tableaux is given. Moreover, some convolution-type identities, which are useful in deriving the Hankel transform of the type 2 ( p, q)-analogue of the r-Whitney numbers of the second kind are obtained. Finally, the Hankel transform of the type 2 ( p, q)-analogue of the r-Dowling numbers are established. Keywords: r-Whitney numbers; r-Dowling numbers; A-tableaux; convolution identities; binomial transform; Hankel transform 1. Introduction Several mathematicians were attracted to work on Hankel matrices because of their connections and applications to some areas in mathematics, physics, and computer science. Several theories and applications of these matrices were established including the Hankel determinant and Hankel transform. The notion of Hankel transform was first introduced in Sloane’s sequence A055878 [1] and was later on studied by Layman [2]. The Hankel matrix H n of order n of a sequence A = {a 0 , a 1 ,..., a n } is defined by H n =( a i+j ) 0i, jn . On the other hand, the Hankel determinant h n of order n of A is defined to be the determinant of the corresponding Hankel matrix of order n. That is, h n = det( H n ). The Hankel transform of the sequence A, denoted by H( A), is the sequence {h n } of Hankel determinants of A. For instance, the Hankel transform of the sequence of Catalan numbers C = { 1 n+1 ( 2n n )} n=1 is given by H(C)= {1, 1, 1, . . .} and the sequence of the sum of two consecutive Catalan numbers, a n = c n + c n+1 with c n , the nth Catalan numbers, has the Hankel transform H( a n )= {F 2n+1 } n=0 , where F n is the nth Fibonacci numbers [2]. One remarkable property of the Hankel transform was established by Layman [2], which states that the Hankel transform of an integer sequence is invariant under binomial and inverse transforms. That is, if A is an integer sequence, B is the binomial transform of A and C is the inverse transform of A, then, Axioms 2021, 10, 343. https://doi.org/10.3390/axioms10040343 https://www.mdpi.com/journal/axioms