i forgot to include d6 x d6, but there are 20 permutations, 16 of which have unique results!! a result of 12 (6x2 or 4x3) or 6 (6x1 or 2x3) are the only repeats. that means 12 and 6 each have 10% chance of being the product of 2d6, every other result has a 1/20 or 5% chance (a 80% chance of getting a unique product) meaning you could effectively use 2d6 as a d20 roll for a result between 1-36