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Enigmas & puzzles

By Ian Stewart   May 2006

Fibonacci’s bank account

It was Saturday evening in the Croesus Club, and two of its members—both bankers—were discussing the previous week’s business.

“We’re thinking of opening seven days a week,” said Werther Packet.

“We did that last week,” replied his friend Ty Koon.

“Did any of your customers use that facility?”

“Just one,” said Ty. “Funny little chap, name of Leo Fibonacci… Always deposits his cash in one-pound coins. Last Sunday he made a deposit, and he made another one on Monday. On Tuesday he made a deposit equal to the sum of the amounts he had deposited…

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