Journal of Integer Sequences, Vol. 22 (2019), Article 19.8.5

A Family of Riordan Group Automorphisms


Ângela Mestre and José Agapito
Centro de Análise Funcional, Estruturas Lineares e Aplicações
Grupo de Estruturas Algébricas, Lineares e Combinatórias
Departamento de Matemática
Faculdade de Cîencias, Universidade de Lisboa
1749-016 Lisboa
Portugal

Abstract:

In 2006, Bacher introduced a family of Riordan group automorphisms parametrized by three complex numbers. Bacher's family is a subgroup of the group of automorphisms of the Riordan group and so is the subfamily parametrized only by two real numbers. Here, we study some of the algebraic properties of this subfamily and use the elements to point out isomorphisms between Riordan subgroups. In this context, we prove that the set of Riordan arrays whose row sum sequence is a sequence of partial sums, forms a Riordan subgroup. Moreover, we show that the well-known recursive matrices may be constructed from sequences of images of a Riordan array under automorphisms. Our construction also discloses a correspondence between the recursive matrices and a pair of well-defined Riordan arrays.


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(Concerned with sequences A000012 A000027 A000045 A000096 A000108 A001478 A005586 A007318 A014137 A014138 A090826 A110555 A115140.)


Received July 10 2019; revised versions received December 23 2019; December 24 2019. Published in Journal of Integer Sequences, December 26 2019.


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