The Cantor set

The Cantor set is the limit of an iterative process, or more precisely the intersection of an infinite sequence of sets. Each step is a set composed of intervals: to get the next one, remove the middle third from each interval.

Forget about that infinite limit stuff: we only care about the first few iterations!

Mathematical descriptions of the Cantor set are awkward and don't seem to arise from or provide any useful intuition. Can APL do better?