... distance-regular graphs. Inci-dentally, descendents have been applied to the Erd˝os–Ko–Rado theorem in extremal set theory [31, Theorem 3], and implicitly to the Assmus–Mattson theorem in coding theory [32, ... hypergeometricorthogonal polynomials 1by the duality properties of Γ. The starting point of the researchpresented in this paper is a result of Hosoya and Suzuki [20, Proposition 1.3] which givesa system of linear ... Contributions to the theory of distance regular graphs, Ph.D. Thesis,Eindhoven University of Technology, Eindhoven, The Netherlands, 1990.[24] D. A. Leonard, Orthogonal polynomials, duality and association...