If you take a positive integer number and divide it by 2 if it is even, or multiply it by 3 and add 1 if it is odd, is it true that eventually you get down to 1? For example, 26-> 13 -> 40 -> 20 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1. During the talk, we will see at least what you can expect on average...