Collatz Conjecture Visualization

The Collatz Conjecture states a simple maths algorithm:
1. Take any number and call it _a_
2. If _a_ is even, then set _a_ equal to _a / 2_. Otherwise, if _a_ is odd, then set _a_ equal to _3a + 1_
3. Repeat step 2

This trivial problem is famous because it has never been proven if every plotted integer converges to 1. You could do a problem that desings a tree starting with 1 and building its way up.

Further Reading:
http://swimmingthestyx.com/?p=447
https://www.jasondavies.com/collatz-graph/
https://en.wikipedia.org/wiki/Collatz_conjecture#In_reverse
http://mathematica.stackexchange.com/questions/85718/trying-to-visualize-the-collatz-conjecture

It seemed easy until I started programming it.