Hahn multiple orthogonal polynomials of type I: Hypergeometrical expressions

Abstract: Explicit expressions for the Hahn multiple polynomials of type I, in terms of Kamp\'e de F\'eriet hypergeometric series, are given. Orthogonal and biorthogonal relations are proven. Then, part of the Askey scheme for multiple orthogonal polynomials type I is completed. In particular, explicit expressions in terms of generalized hypergeometric series and Kamp\'e de F\'eriet hypergeometric series, are given for the multiple orthogonal polynomials of type I for the Jacobi-Pi~neiro, Meixner I, Meixner II, Kravchuk, Laguerre I, Laguerre II and Charlier families.