Question 152
Determine all sets $M$ of natural numbers such that for every two (not necessarily different) elements $a, b$ from $M$ too
$$
\frac{a+b}{\operatorname{ggT}(a, b)}
$$
located in $M$.
$$
\frac{a+b}{\operatorname{ggT}(a, b)}
$$
located in $M$.