Collatz conjecture

collatz.py

import sys


# Take any positive integer n.
# If n is even, divide it by 2 to get n / 2.
# If n is odd, multiply it by 3 and add 1 to obtain 3n + 1.
# The conjecture is that no matter what number you start with, you will always eventually reach 1.

def collatz(n):
    if n % 2 == 0:
        return n / 2
    else:
        return ((n * 3) + 1) / 2


if __name__ == '__main__':
    n = int(sys.argv[1])

    if n < 0:
        sys.exit('N should be a positive integer.')

    count = 0

    while n != 1:
        print(n)
        n = collatz(n)
        count += 1

    print('Operation took ' + str(count) + ' steps.')