Graph Coloring · Superchallenge problem

The Möbius ladder $M_{2n}$ has a cycle of length $2n$ on vertices $1,\ldots,2n$, together with the $n$ "diameters" joining each vertex $i$ ($1\le i\le n$) to the opposite vertex $i+n$. For how many integers $n$ with $4 \le n \le 9$ is $M_{2n}$ bipartite?