This topic is old, and I am far too lazy to go back and look for what answers were posted. The best way to go about this is to find all without the restriction on at least one number and then take away all those that don't have a number. That is, you have 36^10-26^10 = (36^5-26^5)(36^5+26^5) = 48,584,800x72,347,552 = 3,514,991,344,409,600. The factoring was an attempt to not get errors due to tenth powers being too large, but I needed Mathematica anyways. The problem with just trying 10x35^9 is that you restrict where you are placing the number. This would seem to multiply your value by 10 again for each of the places it can be placed, but then you're counting some possibilities more than once. For example, 12b1 changed to 2b11 gives you something you already would have counted. Thus in cases where you have "at least", you want to start with total cases and subtract those away that don't satisfy the "at least" factor.