Question 37
Let $\left(a_{n}\right)_{n \geqslant 1}$ be an increasing sequence of strictly positive integers and $k$ a strictly positive integer. Suppose for some $r \geqslant 1$, ON $\frac{r}{a_{r}}=k+1$. Show that there is an integer $s \geqslant 1$ such as $\frac{s}{a_{s}}=k$.