Project Euler #47 Distinct primes factors

#The first two consecutive numbers to have two distinct prime factors are:

#14 = 2 x 7
#15 = 3 x 5

#The first three consecutive numbers to have three distinct prime factors are:

#644 = 2 x 2 x 7 x 23
#645 = 3 x 5 x 43
#646 = 2 x 17 x 19.

#Find the first four consecutive integers to have four distinct prime factors.
# What is the first of these numbers?

def primes_sieve(limit):
    a = [True] * limit                          # Initialize the primality list
    a[0] = a[1] = False

    for (i, isprime) in enumerate(a):
        if isprime:
            yield i
            for n in xrange(i*i, limit, i):     # Mark factors non-prime
                a[n] = False

def primeFactors(n):
    """Return a list of the prime factors for a natural number."""
    if n == 1: return [1]

    primes = primes_sieve(int(n**0.5) + 1)

    factors = []

    for p in primes:
        if p*p > n:
            break
        while n % p == 0:
            factors.append(p)
            n //= p
    if n > 1:
        factors.append(n)

    return factors


integers = []
start = 210 #smallest number with 4 distinct prime factors 2*3*5*7
while len(integers) != 4:
    #print start
    if len(set(primeFactors(start))) == 4 and\
       len(set(primeFactors(start+1))) == 4 and\
       len(set(primeFactors(start+2))) == 4 and\
       len(set(primeFactors(start+3))) == 4:
        integers = [start,start+1,start+2,start+3]
    start += 1
print integers