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Seive of Eratosthenes

This is an algorithm for finding all prime numbers
up to some limit *n*. You start with a list of all the integers between
2 and *n*:

Then you take the first number as the first prime,
and delete from the list all multiples of that prime:

Repeat with the next number still in the list:

And so on...

When you finish, you have gotten all the primes
from the list.