N=19 (and likely N=18 etc) could also be more uniform if it already jumped to M=2, so that it would be like N=20 except with five points on the inner ring. Or m

N=19 (and likely N=18 etc) could also be more uniform if it already jumped to M=2, so that it would be like N=20 except with five points on the inner ring. Or maybe with six on the inner and twelve on the outer. Would probably be fairly easy to turn this into an optimization problem if one wanted a really uniform distribution (eg. distribute points on rings such that some sum of squared distances is minimized).