 Barban–Davenport–Halberstam theorem

The Barban–Davenport–Halberstam theorem is a result in number theory, specifically in the area of additive number theory and the distribution of prime numbers. It provides a way to estimate the size of the prime numbers in certain ranges. More formally, the theorem deals with the distribution of prime numbers in arithmetic progressions and gives a bound on the number of primes in intervals of certain lengths.