def pfactors(n):
    def find_factor(t):
        (_, n) = t
        if(n == 1):
            return (None, None)
        f = toolz.first(itertools.dropwhile(lambda x: n % x != 0, primes()))
        return (f, n/f)
    return list(toolz.drop(1, map(toolz.first, itertools.takewhile(
        lambda x: x != (None, None), toolz.iterate(find_factor, (0,n))))))