Elementary Number Theory: Sieve of Eratosthenes

This video explains two versions of the Sieve of Eratosthenes, together with its animations. An implementation of such algorithm is given in Pari/GP.

Time stamps
0:42 Some background
2:42 Sieve version 1 (animation)
7:40 Sieve version 2 (animation)
11:09 Explanation on the algorithm
13:28 Implementation in Pari/GP

Proof: Any composite number has a divisor less than the square root of "n"
(it is not the same but similar)

Code for Pari/GP