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# Prove this by combinatorics

Call $$\varphi(n)$$ is an arithmetic function that counts the positive integers less than or equal to $$n$$ that are relatively prime to $$n$$.

By using combinatorics, prove that : $\large \sum_{d|n}\varphi (n) =n$

Note by Rony Phong
2 years, 2 months ago