Diaschisma

2048/2025, the diaschisma, an interval of 19.553 cents, it is the difference between four perfect fifths plus two major thirds and three octaves, Tempering it out leads to Diaschismic temperament. It may also be defined as the difference between a just Pythagorean minor seventh and a just augmented sixth (E.A. 16/9 - 225/128), as the difference between two diatonic semitones and the major whole tone, that is, (9/8)/(16/15)^2, or as the difference between the 5-limit tritone 45/32 and its enharmonic equivalent 64/45.