So we call this a Geometric Sequence with common ratio 2. That just means that if you take any term in the thickness sequence and divide it by the previous term, you'll get 2. If you put one grain of rice in the first square on a chessboard, and then two grains on the next one, four on the next, eight on the next, then sixteen, etc. A way big huge amount. And I'm not kidding.
Geometric growth is fast.
Another interesting thing about this problem is that you'll get basically the same number of folds no matter what kind of sheet you use. The mathematician would say that the first term of a Geometric Sequence doesn't affect its growth rate very much. For instance, if you started with a piece of paper that was twice as thick, you should be able to fold it one fewer time. Not half as many times, but only one fewer. That's not much difference.