Twin prime conjecture
Twin primes are prime numbers that differ by two. For example, 3 and 5 are both prime and differ by two. They are twin primes. 23 is prime, but it is not a twin prime. The primes nearest to 23 are 19 and 29. Twin primes were discovered by Euclid in 300 B.C.
Since Euclid's time mathematicians have wondered whether there are an infinite number of twin primes. Many mathematicians are still trying to find the answer.
- McKee, Maggie (14 May 2013). "First proof that infinitely many prime numbers come in pairs". Nature: International weekly journal of science. Retrieved 9 July 2018.