Problem

Source: First Saudi Arabia JBMO TST 2019, P3

Tags: number theory



How many natural numbers $n$ satisfy the following conditions: i) $219<=n<=2019$, ii) there exist integers $x, y$, so that $1<=x<n<y$, and $y$ is divisible by all natural numbers from $1$ to $n$ with the exception of the numbers $x$ and $x + 1$ with which $y$ is not divisible by.