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has been cited by the following article:

• TITLE: Generalized Powers of Substitution with Pre-Function Operators

  AUTHORS: Laurent Poinsot

  KEYWORDS: Formal Power Series; Formal Substitution; Riordan Group; Generalized Powers; Sheffer Sequences; Umbral Calculus

  JOURNAL NAME: Applied Mathematics, Vol.4 No.7A, July 5, 2013

  ABSTRACT: An operator on formal power series of the form S μS , where μ is an invertible power series, and σ is a series of the formt+（t2）is called a unipotent substitution with pre-function. Such operators, denoted by a pair (μ ，σ ） , form a group. The objective of this contribution is to show that it is possible to define a generalized powers for such operators, as for instance fractional powers σ for every .