Combinations
Computes all possible combinations of n objects taken k at a
time.
Combinations(n, k)
| n | a number. | 
| k | a number less than or equal to  | 
Returns a matrix containing the possible combinations of n
objects taken k at a time.
Combinations(5,2)
    # The columns in the matrix list the values of the 10 possible
    # combinations of 5 things taken 2 at a time.Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.