Eratosthenes, Sieve of

a method in number theory named after Eratosthenes. It consists in the sifting out, or removal, of those whole numbers of a given sequence a₁, a₂, . . ., a_N (for example, the sequence of natural numbers) that are divisible by at least one prime smaller than N^a, where 0 < α ≤ ½. The sieve of Eratosthenes was introduced as a theoretical method of investigation in 1920 by the Norwegian mathematician V. Brun.