Label each item in your group in some defined order. Since order doesn’t matter, as you repeatedly sample r times with replacement you can always write down your outcomes sorted from low to high placement. Finally, separate like values by some symbol, say "|", and consider each of the n distinct objects as indistinct *’s. There will be n-1 of these separators since there will be n to choose from. For example, if choosing r=6 times from the set {a, b, c, d}, then the outcome b, b, a, d, a, b could be collected as a, a, b, b, b, d and written in our code as **|***||* . Notice that shuffling around the identical *’s would not change the code (and similarly for the identical |’s) but swapping a * with a | would be a different outcome. Therefore, we can consider this to be a multinomial coefficient 3.3.5 and the number of ways to rearrange this code is