Summary: Initially, this paper is a discrete analogue of the work of B. M. Brown
, D. K. R. McCormack
, W. D. Evans
and M. Plum
[Proc. R. Soc. Lond., Ser. A, Math. Phys. Eng. Sci. 455, No. 1984, 1235–1257 (1999; Zbl 0944.34018
)] on second-order differential equations with complex coefficients. That is, we investigate the general non-self-adjoint second-order difference expression
where the coefficients
are complex and
is the forward difference operator, i.e.
. Properties of the so-called Hellinger-Nevanlinna m-function for the recurrence relation
, where the
are real and positive, are examined, and relationships between the properties of the
-function and the spectrum of the associated operator are explored. However, an essential difference between the continuous and the discrete case arises in the way in which we define the operator natural to the problem. Nevertheless, analogous results regarding the spectrum of this operator are obtained.