Abstract:
We consider the product of two classical Meixner weight functions whose arguments are shifted with respect to each other. Its restriction to the corresponding integer lattices generates a system of two discrete weights. Under certain conditions on the parameters, this system is perfect and has positive weights. Nevertheless, it is neither an Angelesco system nor a Nikishin system. The corresponding orthogonal polynomials are known to satisfy a four-term recurrence relation for the step-line indices. In this paper, we find explicit expressions for the coefficients of these relations. Passing to limits then yields the coefficients of four-term recurrence relations for a few other families.