Question 68
Find all natural numbers $n$ such that:
$$
\sum_{\substack{d \mid n \\ 1 \leq d \lt n}} d^{2} = 5(n+1)
$$
$$
\sum_{\substack{d \mid n \\ 1 \leq d \lt n}} d^{2} = 5(n+1)
$$
MathNet 2016-part-06 — 184 problems (EN–VI) Question 68
Math Olympiad Vault · MathNet 2016-part-06 — 184 problems (EN–VI)