text: from multiprocessing.pool import Pool
  import time
  
  t =time.time()
  LIMIT_NUM = 5*(10**7)
  
  
  def is_prime(n):
      print(n)
      num = 2*n*n-1 # t(n)
      for i in range(2, int(num**0.5+1)):
          if num % i == 0:
              return 0
      return 1
  
  
  p = Pool(processes=8)
  num_range = range(2, LIMIT_NUM)
  result_list = p.map(is_prime, num_range)
  p.close()
  p.join()
  print(sum(result_list))
  
  
  print('time:'+str(time.time()-t))
  