  This paper presents a first result of a long term research project dealing
with the construction of d-orthogonal polynomials with Hahn's property. We
shall show that the latter class could be characterized by expanding a
polynomial as a finite sum of first derivatives of the elements of the sequence
and we shall explain how this characterization could be used to construct
Hahn-classical d-orthogonal polynomials as well. In this paper we look for
solutions of linear combinations of the first derivatives of two consecutive
elements of the sequence by considering the derivative operator and Delta
(discrete) operator. The resulting polynomials constitute a particular class of
Laguerre d-orthogonal polynomials and a generalization of Mittag-Leffler
polynomials, respectively.
