Stephens' constant
Stephens' constant expresses the density of certain subsets of the prime numbers. Let and be two multiplicatively independent integers, that is, except when both and equal zero. Consider the set of prime numbers such that evenly divides for some power. The density of the set relative to the set of all primes is a rational multiple of
Stephens' constant is closely related to the Artin constant that arises in the study of primitive roots.
