The Tetranacci sequence of numbers is a modified version of the Fibonacci sequence of numbers. The Tetranacci numbers start with four predetermined terms, each term afterwards being the sum of the preceding four terms. The first few Tetranacci numbers are:

0, 0, 0, 1, 1, 2, 4, 8, 15, 29, 56, 108, 208, 401, 773, 1490,

1) Write a lisp program that computes the Tetranacci numbers using:

a) an iterative approach

b) a recursive approach

2) Test both implementations of part 1 for

Tetranacci(10), Tetranacci(20), etc. in increments of 10 up to Tetranacci (100) or higher and comment your results.