PF:
    PF: Reduced denominator's prime factorization is only 2s and 5s ↔ terminating decimal.

A fraction is reducible if its numerator and denominator have any common factor>1, i.e. their prime factorizations are not disjoint, the numerator and denominator are not coprime, GCF≠1.
Irreducible if prime factorizations are disjoint, the numerator and denominator are coprime, GCF=1.
1/d and d-1/d (and improper d+1/d) are not reducible. [A pair of consecutive numbers is coprime.]
A proper fraction can be written as a sum of distinct unit fractions (1/n), i.e. as an Egyptian fraction. E.g. 5/8=1/2+1/8 43/48=1/2+1/3+1/16 3/7=1/3+1/11+1/231
   Egyptian denominators: (for proper fractions only)

Experiment: generate all fractions of denominators 2-D. Count #, #reducible, #terminating decimals.
D:

#total fractions: - #reducible: = #actual/unique fractions:
#total terminating decimals: - #terminating reducibles: = actual # terminating decimals:

All fractions (reduced): Show? Yes No

A reduced fraction with a prime denominator p, the numerator can be all numbers from 1 to p-1.