I don't know if this is considered a research question but I stumbled upon collecting formulae 1 for $n=\frac{xyz}{x+y+z}$ and the question is:
Does the diophantine equation $xyz=n(x+y+z)$ for given $n\in \mathbb{N}$ have only finitely many solutions $x,y,z\in \mathbb{N}$ or is there a $n$ such that it has infinitely many solutions?