Clean chain calculation

clean_chain.py

import itertools


def generate_prime():
    d = {}
    for i in itertools.count(2):
        n = d.pop(i, None)
        if n:
            p = n + i
            while p in d:
                p += n
            d[p] = n
        else:
            yield i
            d[i * i] = i


def clean_chain(seq_num):
    prime_sum = 0
    valid_chain_counter = 0
    seq_length = 0

    for e in generate_prime():
        seq_length += 1
        print e, prime_sum
        prime_sum += e
        if prime_sum % e == 0:
            valid_chain_counter += 1
        if valid_chain_counter == seq_num:
            break

    return seq_length

if __name__ == "__main__":
    print clean_chain(4)
    print "---------------------------------------------------"
    print clean_chain(5)