project-euler/187_semiprimes.py

#!/usr/bin/env python3

def primes(n):
    count = 0
    sieve = [False]*n
    for p in range(2, n):
        if sieve[p]:
            continue
        for i in range(p**2, n, p):
            sieve[i] = True
        np = 2*p
        for p2 in range(2,p+1):
            if np >= n:
                break
            if not sieve[p2]:
                count += 1
            np += p
    return count

print(primes(10**8))