Look-ahead methods for block Hankel systems

In this paper, the updating formulas used by three look-ahead methods for solving Hankel systems are generalized to the square block case. Each of the original methods was described in the literature using the terminology of different but strongly related fields: formal orthogonal polynomials, Padé approximants, structured matrices. This paper gives several of these connections generalized to the block case and shows that each viewpoint has its own merits.