• + 4 comments

    isn't the question bit wrong?? if n=2 then there are 4 combinations and 2 non-zero stones. On the other hand when n=4 there are 8 combinations which means only 3 non-zero stones, in this case n should be 3. and if n=4 then there are 16 combinations because there are 4 non-zero stones.

    Somebody explain.