In this assignment, you will write a program calculates [Tetranacci numbers](http://mathworld.wolfram.com/TetranacciNumber.html).
The formula for the `n`th Tetranacci number **T<subn</sub** is defined as follows:
- T<sub0</sub = 0
- T<sub1</sub = 1
- T<sub2</sub = 1
- T<sub3</sub = 2
- T<subn</sub = T<subn-1</sub + T<subn-2</sub + T<subn-3</sub + T<subn-4</sub
You need to complete following tasks:
1. Your task is to implement a recursive function `tetranacci` which accepts an integer `n` (you may assume that `n = 0`), and computes the `n`-th Tetranacci number.
2. Print on the screen first 10 Tetranacci numbers.
