def problem10():
n = 2000000
primes_below_n = itertools.takewhile(lambda p: p < n, gen_primes())
return sum(primes_below_n)
def problem7():
gen = enumerate(gen_primes())
gen = itertools.dropwhile(lambda e: e[0] < 10001, gen)
gen = itertools.imap(lambda e: e[1], gen)
return gen.next()