Help me solve this math , algorithm problem. Really interest

Question

Prompt the user for amount of possible numbers, the user types the numbers and then the program needs to display all the possibilities of those numbers.

For example:

Program prompts the user for amount of numbers,
lets say user types 3 
Then he user has to type 3 different numbers
Lets say user types 1,2,3
Now the program needs to show all possible numbers out of those 3 numbers
so it would be 1,2,3, 12,13,21,31,23,32, etc you get the general idea.