I have $K$ variables.
Each variable can take any value form a set with $N$ elements.
We have $N^K$ possible solutions (permutations with repetition, when at each time slot we can choose among $N$ elements each time). However, some of these $N^K$ possible solutions will provide the same offered rate (we do not care about the ordering). So, the possible solutions reduce to:
How can I generate all these possible combinations when $N=7$, $K=20$?