256/243
256/243 |8 -5>
90.225 cents
The Pythagorean limma, or Pythagorean semitone, is the interval of size 256/243 = 2^8/3^5 (about 90.2¢), which is the diatonic semitone in Pythagorean tuning. It can be generated by stacking five 4/3 just perfect fourths and octave-reducing the resulting interval.