If 1/8" equals one unit then you have (in the opposite order), 1,2,3,5,8,13,21. Each number being the sum of the two proceeding. This usually starts with two number 1s, so 1,1,2,3,5,8,13,21 and is a common simplification of the golden mean often used by woodworkers.
BUT, as to what sizes are normally used, that would probably be the sizes that one has at the bench.