input: Write a Python function to implement the Sieve of Eratosthenes to find all prime numbers up to a given number.
  assert primeSieve(10) == [2, 3, 5, 7]
  assert primeSieve(20) == [2, 3, 5, 7, 11, 13, 17, 19]
  assert primeSieve(30) == [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
output: def primeSieve(n):
      is_prime = [True] * (n + 1)
      p = 2
      while p * p <= n:
          if is_prime[p]:
              for i in range(p * p, n + 1, p):
                  is_prime[i] = False
          p += 1
      return [p for p in range(2, n + 1) if is_prime[p]]