Understanding powers and indices (simply)

[bplus]

OK here is what Internet said about Grains of sand:
   

But what if you got the rice from each square when doubling amount for each square =
1 or 2 ^ 1 - 1
1 + 2 = 3 or 2 ^ 2 - 1
1 + 2 + 4 = 7 or 2 ^ 3 - 1
1 + 2 + 4 + 8 = 15 or 2 ^ 4 - 1
...
1 + 2 + 4 + 8 + .... + 9,223,372,036,854,775,808 = 2 ^ 64 - 1 = 18,446,744,073,709,551,615