The Pythagoreans were not the first to think of suggesting a pattern of numbers as key to the distances between the heavenly bodies (Anaximander had already made that breakthrough, a little ahead of Pythagoras). But in the Pythagorean speculations we can see that the notion of harmony, and the power of simple ratios in the tetraktys, has encouraged them to suggest that perfect patterns are what we would expect.

Presocratic Philosophy: A Very Short Introduction (2004) - Ch. 6 : Pythagoras and other mysteries