Question 11
Find all natural $a$ such that there exist prime numbers $p, q, r$ so that
$$
a = \frac{p+q}{r} + \frac{q+r}{p} + \frac{r+p}{q}.
$$
$$
a = \frac{p+q}{r} + \frac{q+r}{p} + \frac{r+p}{q}.
$$
MathNet 2014 Question 11
Math Olympiad Vault · MathNet 2014