Prime numbers generator explanation? [duplicate]

Question

I was searching for an algorithm to generate prime numbers. I found the following one done by Robert William Hanks. It is very efficient and better than the other algorithms but I can not understand the math behind it.

def primes(n):
    """ Returns  a list of primes < n """
    lis = [True] * n
    for i in range(3,int(n**0.5)+1,2):
        if lis[i]:
            lis[i*i::2*i]=[False]*int((n-i*i-1)/(2*i)+1)
    return [2] + [i for i in range(3,n,2) if lis[i]]

What is the relation between the array of Trues values and the final prime numbers array?

Answer 1

Starting with n True values in an array, with i enumerated from 3 to sqrt(n) by the step of 2, if the ith entry in the array is still True, set to False all entries from i^2 to the end of the array by the step of 2*i (these all will be multiples of i).

All odd True entries above 1 that are left in the array in the end, are prime.

All thus found numbers, and 2, are all the prime numbers that exist below n.