Koornwinder polynomials

Koornwinder polynomials are a class of orthogonal polynomials that generalize the basic hypergeometric orthogonal polynomials. They are associated with the root system of type \(C_n\) and are connected to various areas in mathematics, including special functions, combinatorics, and representation theory. The Koornwinder polynomials can be defined using a particular q-orthogonality relation and are characterized by parameters that provide additional flexibility compared to the classical orthogonal polynomials.