Δ-Coherent pairs and orthogonal polynomials of a discrete variable

27 pages, no figures.-- MSC1991 codes: 33C25; 42C05.MR#: MR1949214 (2003m:33009)Zbl#: Zbl 1047.42019In this paper we define the concept of D-coherent pair of linear functionals. We prove that if (u_0, u_1) is a D-coherent pair of linear functionals then at least one of them must be a classical discrete linear functional under certain conditions. Examples related to Meixner and Hahn linear functionals are given.F. Marcellán wishes to acknowledge Dirección General de Investigación (MCYT) of Spain for financial support under grant BFM2000-0206C04-01 and INTAS project 2000-272.Publicad