Sieve of Eratosthenes

Sieve of Eratosthenes, mathematical process for discovering prime numbers. The ancient Greek mathematician Eratosthenes worked out this method by which whole numbers are eliminated—as if filtered through a sieve—until only prime numbers (those that can be divided evenly by themselves and 1) remain. The sieve starts as a string of consecutive whole numbers, beginning with 2. Every even number (except 2 itself) is eliminated, since each of them can be divided by 2. Next, beginning after the first untouched number after 2 (namely 3), every third number is eliminated, because they can all be divided evenly by 3. The next prime is the next untouched number. Since there is no largest prime number, the process can go on indefinitely.

See also: Eratosthenes.