A kind of orthogonal polynomials and related identities (1606.08327v3)

Abstract: In this paper we introduce the polynomials ${d_n^{(r)}(x)}$ and ${D_n^{(r)}(x)}$ given by $d_n^{(r)}(x)=\sum_{k=0}^n\binom{x+r+k}k\binom{x-r}{n-k} \ (n\ge 0)$, $D_0^{(r)}(x)=1,\ D_1^{(r)}(x)=x$ and $D_{n+1}^{(r)}(x)=xD_n^{(r)}(x)-n(n+2r)D_{n-1}^{(r)}(x)\ (n\ge 1).$ We show that ${D_n^{(r)}(x)}$ are orthogonal polynomials for $r>-\frac 12$, and establish many identities for ${d_n^{(r)}(x)}$ and ${D_n^{(r)}(x)}$, especially obtain a formula for $d_n^{(r)}(x)^2$ and the linearization formulas for $d_m^{(r)}(x)d_n^{(r)}(x)$ and $D_m^{(r)}(x)D_n^{(r)}(x)$. As an application we extend recent work of Sun and Guo.