Sixteen

            “Put one grain of barley upon the first square, and double that upon the second.  Keep doubling the number of grains on each subsequent square.  How many should you have upon the fifth square, Estel?”

            The boy held up one finger, a second, and then a third, mouthing a number as he raised each one.  As he raised the fifth finger, Erestor could see the expression of triumph in his eyes.  “Sixteen!” Estel exclaimed.  “And on the next thirty-two, and then sixty-four….”  He paused.  “Soon,” he said thoughtfully, “they would not fit upon the chessboard.  You would need a cart!”