Conjectured primality test

cop.py

# Author: Pedja 



print("                        ***** COP *****\n\n\n")
while True:
	
    
   
    n=int(input("Enter a number : "))
	
    def test(n):
        s=0
        for k in range(1,n):
            s=s+pow(2**k-1,n-1,2**n-1)
        return s%(2**n-1)==n
	
	


   
    if n<3:
        print("Number must be greater than two")
    elif n==9:
        print(str(n)+" is pseudoprime")
    else:
        if test(n):
            print(str(n)+" is prime")
        else:
            print(str(n)+" is composite")
    
		
    try_again = ""
    # Loop until users opts to go again or quit
    while not(try_again == "1") and not(try_again == "0"):
        try_again = input("Press 1 to try again, 0 to exit. ")
        if try_again in ["1", "0"]:
            continue  # a valid entry found
        else:
            print("Invalid input- Press 1 to try again, 0 to exit.") 
    # at this point, try_again must be "0" or "1"
    if try_again == "0":
        break