In mathematics, the discrete q-Hermite polynomials are two closely related families h_n(x;q) and ĥ_n(x;q) of basic hypergeometric orthogonal polynomials in the basic Askey scheme, introduced by Al-Salam and Carlitz (1965). Roelof Koekoek, Peter A. Lesky, and René F. Swarttouw (2010, 14) give a detailed list of their properties. h_n(x;q) is also called discrete q-Hermite I polynomials and ĥ_n(x;q) is also called discrete q-Hermite II polynomials.

This article may be too technical for most readers to understand. (April 2017)

The discrete q-Hermite polynomials are given in terms of basic hypergeometric functions and the Al-Salam–Carlitz polynomials by

${\displaystyle \displaystyle h_{n}(x;q)=q^{\binom {n}{2}}{}_{2}\phi _{1}(q^{-n},x^{-1};0;q,-qx)=x^{n}{}_{2}\phi _{0}(q^{-n},q^{-n+1};;q^{2},q^{2n-1}/x^{2})=U_{n}^{(-1)}(x;q)}$

${\displaystyle \displaystyle {\hat {h}}_{n}(x;q)=i^{-n}q^{-{\binom {n}{2}}}{}_{2}\phi _{0}(q^{-n},ix;;q,-q^{n})=x^{n}{}_{2}\phi _{1}(q^{-n},q^{-n+1};0;q^{2},-q^{2}/x^{2})=i^{-n}V_{n}^{(-1)}(ix;q)}$

and are related by

${\displaystyle h_{n}(ix;q^{-1})=i^{n}{\hat {h}}_{n}(x;q)}$

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