> That goal is the proof to a conjecture concerning prime numbers. > Those are the whole numbers that are divisible only by one and > themselves. Primes abound among smaller numbers, but they become less > and less frequent as one goes towards larger numbers. In fact, the > gap between each prime and the next becomes larger and larger ? on > average. But exceptions exist: the ?twin primes?, which are pairs of > prime numbers that differ in value by 2. Examples of known twin > primes are 3 and 5, or 17 and 19, or 2,003,663,613 × 2^195,000 ? 1 and > 2,003,663,613 × 2^195,000 + 1. > > The twin prime conjecture says that there is an infinite number of > such twin pairs. Some attribute the conjecture to the Greek > mathematician Euclid of Alexandria, which would make it one of the > oldest open problems in mathematics.