The Pythagorean Scale is known as a 3-limit tuning. This means that the numbers making up the ratios must be multiples of prime numbers not greater than 3. That's why it doesn't have the simple ratio 5:4 for the third scale degree found in the Classic Just scale.
C 2:1
B 243:128
A 27:16
G 3:2
F 4:3
E 81:64
D 9:8
C 1:1
