The rule is if the number is odd then you will multiply by 3 and add 1 if it is even then divide by 2. At the end it is supposed to end at one before repeating with one 4 2 1. You can type any non-negative integer in here except for zero.
This is the speed version if you don't have time use this number for something cool 63728127 regular version https://scratch.mit.edu/projects/1072968346/