Collatz conjecture

The 3x + 1 problem or Collatz conjecture is simple in its formulation but until now no proof is known that it is in fact true for any n. A conjecture is generally believed true but a formal proof is still to be found.

The conjecture says that if you repeatedly apply the following rule to a number the end result will always be one (1):
- if even then divide by 2;
- if odd then multiply by 3 and add 1.

Example:
9
28
14
7
22
11
34
17
52
26
13
40
20
10
5
16
8
4
2
1

Take any number and try it.

What about 27?