title: Combinations of integers
body: <p>I'd appreciate any help on the following problem. I have n integers from 0 to n-1, and I'm trying to generate a list of all possible combinations of length k (i.e. k concatenated integers) such that every pair of consecutive integers are not equal. So, for example, (1)(2)(3)(2) would be valid with k = 4, but (1)(2)(3)(3) would not be valid. Any ideas on how to approach this most efficiently? (I don't care much about length/degree of complexity of the code, just efficiency)</p>