Doubling grains of wheat on a checkerboard

A few years ago, the Museum of Science and Industry in Chicago had a fascinating display. It showed a checkerboard with 1 grain of wheat on the first square, 2 on the second, 4 on the third, then 8, 16, 32, 64, and so on until they could no longer fit the seeds on the square. Then it asked the question, “At this rate of doubling each successive square, how much would you have on the checkerboard by the 64th square?” You could punch a button at the bottom of the display to find out. The answer? “Nine sextillion—enough grain to cover the entire subcontinent of India 50 feet deep.” Incredible! (Our Daily Bread, September 14, 1998).