Collatz_Sequence.py

import sys, time
print('''
    Collatz Sequence, or, the 3n + 1 Problem by sinistergeek
    The Collatz sequence is a sequence of numbers produced from a starting number  n, following three rules:
    1) If n is even, the next number n is n / 2.
    2) If n is odd, next number n is n *3 + 1.
    3) If n is 1, stop.Otherwise, repeat.
    It is generally thought, but so far not mathematically proven,that every starting number eventually terminates at 1.
      ''')
print('Enter a starting number (greater than 0) or QUIT:')
response = input('> ')
if not response.isdecimal() or response == '0':
    print('You must enter an integer greater than 0.')
    sys.exit()
n = int(response)
print(n,end='',flush=True)
while n != 1:
    if n%2 == 0:
        n = n // 2
    else:
        n = 3 * n + 1
    print(', ' + str(n),end='',flush=True)
    time.sleep(0.1)
print()