TITLE: Integer lattice points on a hypersphere
QUESTION [16 upvotes]: Is the following statement true?

For every integer $n\ge2$ and every integer $k\ge0$ there exists a hypersphere in $\mathbb{R}^n$  (circle, sphere etc) containing exactly $k$ integer lattice points on its surface.

REPLY [17 votes]: There are several related and very interesting problems and theorems:  

Schinzel's theorem - solves the problem in $\mathbb{R}^2$ using so-called Schinzel circles. It seems intuitively clear that it generalizes to higher dimensions by slightly adjusting radius of a hypersphere so that it contains exactly the same lattice points as its section in lower dimension, but of course, a rigorous proof is needed. Indeed, there is:
Kulikowski's theorem - gives explicit construction in $\mathbb{R}^3$ and generalizes to all higher dimensions:

W. Sierpiński, "Elementary Theory of Numbers: 2nd English Edition", page 386, the last paragraph:

T. Kulikowski [1] has proved that for any natural number n there 
  exists a sphere (in the three-dimensional space), on the boundary of 
  which there are precisely n points whose coordinates are integers. He 
  generalized this theorem for spheres in spaces of an arbitrary $\ge 3$ 
  dimension.

And similar problems related to interior points:

Steinhaus' theorem
Browkin's theorem