Recurrence relations for the coefficients of the confluent and Gauss hypergeometric functions in the complex plane

TL;DR

This paper derives third-order recurrence relations for the coefficients of confluent and Gauss hypergeometric functions, providing new tools for their analysis and extending to other special functions.

Contribution

It introduces novel third-order recurrence relations for hypergeometric function coefficients, enhancing analytical methods for these functions and related special functions.

Findings

Coefficients satisfy third-order recurrence relations

New approach for studying hypergeometric functions

Extended recurrence relations to other special functions

Abstract

For $a,b,c,z,p, \theta \in \mathbb{C}$, where $\mathbb{C}$ is the complex plane, $-c\notin \mathbb{N\cup }\left\{ 0\right\} $, let \begin{equation*} \mathcal{M}\left( z\right) =\left( 1-\theta z\right) ^{p}M\left(a;c;z\right) =\sum_{n=0}^{\infty }u_{n}z^{n}, \end{equation*} where $|z| <\frac{1}{\theta}$, $|\arg (1-\theta z)| < \pi$, and let \begin{equation*} \mathcal{G}\left( z\right) =(1-\theta z) ^{p}F(a,b;c;z) =\sum_{n=0}^{\infty }v_{n} z^{n}, \end{equation*} where $|z| < 1$, $|\arg (1-\theta z)| < \pi$. In this paper, we prove that the coefficients $u_{n}$ and $v_{n}$ for $n\geq 0$ satisfy a 3-order recurrence relation. These offer a new way to study confluent hypergeometric function $M(a;c;z)$ and Gauss hypergeometric function $F(a,b;c;z)$. And we provide other special functions' recurrence relations of their coefficients, such as error function, Bessel function, incomplete gamma function, complete elliptic integral and Chebyshev polynomials.