Brushless AC generator types and their winding
A magnetic field always has a north and a south pole. Hence, you can't have an odd number of poles in any winding. 

Even if you hypothetically did manage to come up with a way to do it, the poles are distributed around on a circle. Let's say we make 7 poles - you could then have say N S N S N S N . However, since they are on a circle, the first and the last N would be the same, and would just appear as one big N. Hence, you still end up with en even number of poles. 

You can have a odd number of pole-pairs, but that is a different thing.