def prime_sieve_erathosthenes(n):
    """Sieve of Erathosthenes

    Output the list of all primes less than n
    """

    not_prime = []
    prime = []

    if n < 2:
        print("No primes less than 2")
        return 1

    for i in range(2, n+1):
        if i not in not_prime:
            prime.append(i)
            for j in range(i*i,n+1, i):
                not_prime.append(j)

    return prime