Question 153
Find all positive integers $n$ such that
$$
\sum_{k=1}^{n} \phi(k)=\frac{3 n^{2}+5}{8}
$$
$$
\sum_{k=1}^{n} \phi(k)=\frac{3 n^{2}+5}{8}
$$
MathNet 2007-part-03 — 185 problems (EN–VI) Question 153
Math Olympiad Vault · MathNet 2007-part-03 — 185 problems (EN–VI)