Collatz conjecture: take any positive integer - no matter what value, if you follow this formula, you will always end up at number 1.

Formula: n. If even - halve it. If odd, x3 then add 1. Repeat.

def collatz(number):

if number == 0:
    try:
        print('enter a number:')
        number=int(input())
        print("your number is " + str(number))
    except ValueError:
        print("enter an integer")

if number == 1:
    print("the number is now 1")

if number > 1:
    #if number is even
    if number%2 == 0:
        print("this is an even number")
        #print number//2
        number = number//2
        print("divided by two, is " + str(number))
        #re-run on this new number
        collatz(int(number))

    else:
        print("this is an odd number, but is not 1")
        number = ((number*3)+1)
        print("times 3, plus one, is " + str(number))
        #re-run on this new number
        collatz(int(number))