Density of Visible Lattice Points on Hyperplanes and their Intersections

A lattice point $\vec{x}=(x_1,\dots ,x_n)\in {\mathbb{Z}}^n$ is said to be visible if the line segment between $\vec{x}$ and the origin contains no other lattice point. In this paper, we compute the asymptotic density of visible lattice points on hyperplanes and their intersections. In particular, we show that the hyperplane $\vec{a}\cdot \vec{x}=b$ in ${\mathbb{R}}^n$ has visible point density $J_{n-1}(b)\mathrm{/}{b}^{n-1}$ where $J$ is the Jordan totient function. We extend this basic result to find the density of visible points on the intersection of hyperplanes and to the density of $k$-th power free points. Finally, for a fixed dimension $n$, we consider the closure of the set of all possible densities that occur.