@astrid @lily @andrewt What I particularly like is /why/ people get all golden ratio on music (*):
An octave has: Five black notes. Eight white notes. Thirteen notes. 5, 8, 13, Fibonacci, Φ!
Unfortunately, the 8 and 13 double count the first/last note, and it's really about the twelfth root of two.
So you've got a whole branch of musical numerology based on incorrect 1-based indexing!
((*) Sorry, Andrew, if this is what you were referring to, but I didn't see it explicitly mentioned.)