Hankel matrix

Summary

A Hankel matrix is a matrix that is constant along each anti-diagonal, the lines that go from lower left to upper right. Its entry in row $i$ and column $j$ depends only on the sum $i + j$. Hankel matrices appear for moment sequences, for the realisation of linear systems from their impulse responses, and in the theory of orthogonal polynomials. Reversing the order of the rows turns a square Hankel matrix into a Toeplitz matrix.