A prime factoriser

You will write a function that breaks a number into primes, then use it to test for primes and to find numbers in which no prime repeats.

The idea. Divide by $2$ while you can, then by $3$, then by $4$ (which never divides, since the $2$s are gone), and so on, until $1$ is left.

Your tasks.

1. In prime_factors, return the list of prime factors of n, smallest first, with repeats. For $12$ it is [2, 2, 3].
2. In is_prime, return True when n is a prime: it has exactly one prime factor.
3. Fill no_repeats with the numbers of numbers in which no prime appears twice.