Question 148
Prove that for every integer $n$ greater than $1$,
$$
\sigma(n) \phi(n) \leq n^{2}-1
$$
When does equality hold?
$$
\sigma(n) \phi(n) \leq n^{2}-1
$$
When does equality hold?
MathNet 2007-part-03 — 185 problems (EN–VI) Question 148
Math Olympiad Vault · MathNet 2007-part-03 — 185 problems (EN–VI)