13edo

13edo, or 13 equal divisions of the octave, is the equal tuning featuring steps of (1200/13) ~= 92.308 cents, 13 of which stack to the perfect octave 2/1. It does not approximate many small prime harmonics well at all but approximates 10/9, 11/8, 17/13, and 13/8 (more accurately 21/13) well for its size. The approximations do not fit very well in a rank-2 temperament, though, so higher JI (taking advantage of e.g. 13:17:19:21 or 17:20:26:29) or DR-based interpretations are often preferred among 13edo users.