Marinada '24

[lang=hr] Marin je stvarno dao maha svojoj kreativnost, možda malo i previše. Odredi produkt svih prirodnih brojeva $k\geq 2$ za koje je niz definiran sa $a_1 = k$ i $a_n = k \cdot \phi (a_{n-1})$ za $n\geq 2$ ograničen. [/lang] [lang=en] Marin really let his creativity run wild, maybe a bit too much. Determine the product of all natural numbers $k \geq 2$ for which the sequence defined by $a_1 = k$ and $a_n = k \cdot \phi(a_{n-1})$ for $n \geq 2$ is bounded. [/lang]