He doubles at every village. Two men leave the first, four the second, eight the third. Thirty doublings is 2 to the power of 30, which is over a billion men.
A king sends his servant to raise an army from 30 villages. At each village he must take on as many new men as he arrives with. He reaches the first village on his own. How many men, counting himself, leave the thirtieth village?
Give me a hintThe hint
Work out the first three villages and look at the pattern.
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1,073,741,824
Source: Alcuin of York, Propositiones ad Acuendos Juvenes, No. 13, c. 800