Question 146
For each positive integer $n$, let $f(n)$ be either the unique integer $r \in \{0,1, \ldots, n-1\}$ such that $n$ divides $15 r-1$, or $0$ if such $r$ does not exist. Compute
$$
f(16)+f(17)+f(18)+\cdots+f(300) .
$$
$$
f(16)+f(17)+f(18)+\cdots+f(300) .
$$