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MathNet 2024-part-06 — 165 problems (EN–VI) Question 120

Math Olympiad Vault · MathNet 2024-part-06 — 165 problems (EN–VI)

Question 120

For any positive integer $n$, let $f(n)$ be the number of ordered triples $(a, b, c)$ of positive integers such that
- $\max (a, b, c)$ divides $n$ and
- $\operatorname{gcd}(a, b, c)=1$.
Compute $f(1)+f(2)+\cdots+f(100)$.