Asked by: Will Heath, Manchester
There are techniques for finding primes. The oldest is the so-called Sieve of Eratosthenes, named after the eponymous Greek scholar. Starting from 2 – the smallest prime – write down each consecutive number up to some maximum. Strike out every multiple of 2; the first number missed out from this process is then also a prime: 3. Now delete each multiple of 3, and repeat. Those left out each time are the primes.