You'll notice all of those numbers steps contain 107 as the first common number, so everything after 107 is all the same, and with that, you can take and number and, say you wanted to get 50 steps, find the (nSteps - 50)th number up there.

@danpost the video in the description explains why. Two numbers steps may end up at the same result. for instance if you start at 10 you will get 10 -> 5 -> 16 -> 8 - > 4 -> 2 -> 1, and if you start at 21 you will get 21 -> 64 -> 32 -> 16 -> 8... and so on. Heres a small example:
https://occupymath.files.wordpress.com/2017/04/collatz.png?w=700

2018/4/12

Collatz Calculator

2018/4/12

Collatz Calculator

2018/4/12

Collatz Calculator