Distinct primes factors
Problem 47
The first two consecutive numbers to have two distinct prime factors are:
14 = 2 
7
15 = 3 5
The first three consecutive numbers to have three distinct prime factors are:
644 = 2² 7 23
645 = 3 5 43
646 = 2 17 19.
Find the first four consecutive integers to have four distinct prime factors. What is the first of these numbers?
本题考察Python中数组的运用：
n=1000000
a=[0 for i in range(n+1)]
i=2
while i<=n:
if (a[i]==0):
j=2*i
while j<n:
a[j]=a[j]+1
j+=i
i+=1
for i in range(1,n+1-3):
if (a[i]==4 and a[i+1]==4 and a[i+2]==4 and a[i+3]==4):
print i