A chessboard can hide an astonishing number. Put 1 grain of wheat on the first square, 2 on the second, 4 on the third, and keep doubling. After 64 squares, the total is:
1 + 2 + 4 + ⋯ + 2⁶³ = 2⁶⁴ − 1
= 18,446,744,073,709,551,615.
A simple geometric progression turns a handful of grain into an almost unimaginable quantity.