Log-behavior of two sequences related to the elliptic integrals

Abstract

Two interesting sequences arose in the study of the series expansions of the complete elliptic integrals, which are called the Catalan-Larcombe-French sequence $\{P_n{\}}_{n\ge 0}$ and the Fennessey-Larcombe-French sequence $\{V_n{\}}_{n\ge 0}$ respectively. In this paper, we prove the log-convexity of $\{V_n^2-V_{n-1}{V}_{n+1}{\}}_{n\ge 2}$ and $\{n!V_n{\}}_{n\ge 1}$, the ratio log-concavity of $\{P_n{\}}_{n\ge 0}$ and the sequence $\{A_n{\}}_{n\ge 0}$ of Apéry numbers, and the ratio log-convexity of $\{V_n{\}}_{n\ge 1}$.

15 pages