In this paper we construct a cover ${a_{s}(operatorname {mod} n_{s})}_{s=1}^{k}$ of $mathbb {Z} $ with odd moduli such that there are distinct primes $p_{1},ldots ,p_{k}$ dividing $2^{n_{1}}-1,ldots ,2^{n_{k}}-1$ respectively. Using this cover we show that for any positive integer $m$ divisible by none of $3, 5, 7, 11, 13$ there exists an infinite arithmetic progression of positive odd integers the $m$th powers of whose terms are never of the form $2^{n}pm p^{a}$ with $a,nin {0,1,2,ldots }$ and $p$ a prime. We also construct another cover of $mathbb {Z} $ with odd moduli and use it to prove that $x^{2}-F_{3n}/2$ has at least two distinct prime factors whenever $nin {0,1,2,ldots }$ and $xeq a (operatorname {mod} M)$, where ${F_{i}}_{igeqslant 0}$ is the Fibonacci sequence, and $a$ and $M$ are suitable positive integers having 80 decimal digits. [ABSTRACT FROM AUTHOR]