input: Write a python function to check if a number is prime using a list of known prime numbers.
  assert is_prime(2) == True
  assert is_prime(4) == False
  assert is_prime(11) == True
  assert is_prime(15) == False
  assert is_prime(97) == True
output: def is_prime(n):
      if n <= 1:
          return False
      known_primes = [2]
      for prime in known_primes:
          if n == prime:
              return True
          if n % prime == 0:
              return False
      for i in range(3, int(n**0.5) + 1, 2):
          if n % i == 0:
              return False
      return True