The general case on the order of appearance of product of consecutive Fibonacci and Lucas numbers

Abstract

Let $F_n$ and $L_n$ be the $n$th Fibonacci and Lucas number, respectively. For each positive integer $m$, the order of appearance of $m$ in the Fibonacci sequence, denoted by $z(m)$, is the smallest positive integer $k$ such that $m$ divides $F_k$. Recently, D. Marques has obtained a formula for $z(F_n{F}_{n+1})$, $z(F_n{F}_{n+1}{F}_{n+2})$, and $z(F_n{F}_{n+1}{F}_{n+2}{F}_{n+3})$. In this paper, we extend Marques' result to the case $z(F_n{F}_{n+1}\cdots F_{n+k})$ for every $4\le k\le 6$. We also give a formula for $z(L_n{L}_{n+1}\cdots L_{n+k})$ when $k=5,6$ which extends the recent result of Marques and Trojovský. Our method gives a general idea on how to obtain the formulas for $z(F_n{F}_{n+1}\cdots F_{n+k})$ and $z(L_n{L}_{n+1}\cdots L_{n+k})$ for every $k\ge 1$.

Submitted 2 years ago to Contributions to Discrete Mathematics