Given a number of dice N and the number of sides on each die S, write a MATLAB function that will output how many unique permutations you will get.

For example, unique_dice(2,6) will roll two six-sided dice, and should output 21. Although there are 36 possible combinations for two six-sided dice, (1,2) and (2,1) are equivalent, so (1,2) only counts once.

Assume that the dice are fair, and have an equal chance of rolling any number. Good luck!