Question 142
Let $n$ be a given positive integer. Find the least positive integer $u_n$, such that for any positive integer $d$, the number of integers divisible by $d$ in every $u_n$ consecutive positive odd numbers is not less than the number of integers divisible by $d$ in $1, 3, 5, \dots, 2n-1$. (posed by Chen Yonggao)