Why do aircraft radial engines always use an odd number of cylinders?

Factual Questions
2

A. Radials are built with an odd number of cylinders to give a better firing order and corresponding smoothness with lack of vibration.

www.radialengines.com/frequently-asked-questions/

.

3

Wiki’s visuals nail it:

4

Reported. This is the 2nd time today (that I’ve noticed) that a newbie has come in and posted the same question as another poster did just a short while earlier.