"Ten digits," Sophie said, her cryptologic senses tingling as she studied the printout.

　　13-3-2-21-1-1-8-5Grand-père wrote his account number on the Louvre floor!

　　When Sophie had first seen the scrambled Fibonacci sequence on the parquet, she had assumed itssole purpose was to encourage DCPJ to call in their cryptographers and get Sophie involved. Later,she realized the numbers were also a clue as to how to decipher the other lines—a sequence out oforder... a numeric anagram. Now, utterly amazed, she saw the numbers had a more importantmeaning still. They were almost certainly the final key to opening her grandfather's mysterious safe-deposit box.

　　"He was the master of double-entendres," Sophie said, turning to Langdon. "He loved anythingwith multiple layers of meaning. Codes within codes."Langdon was already moving toward the electronic podium near the conveyor belt. Sophie grabbedthe computer printout and followed.

　　The podium had a keypad similar to that of a bank ATM terminal. The screen displayed the bank'scruciform logo. Beside the keypad was a triangular hole. Sophie wasted no time inserting the shaftof her key into the hole.

　　The screen refreshed instantly.

　　ACCOUNT NUMBER: _ _ _ _ _ _ _ _ _ _The cursor blinked. Waiting.

　　Ten digits. Sophie read the numbers off the printout, and Langdon typed them in.

　　ACCOUNT NUMBER: 1332211185When he had typed the last digit, the screen refreshed again. A message in several languagesappeared. English was on top.

　　CAUTION:

　　Before you strike the enter key, please check the accuracy of youraccount number.

　　For your own security, if the computer does not recognize youraccount number, this system will automatically shut down.

　　"Fonction terminer," Sophie said, frowning. "Looks like we only get one try." Standard ATMmachines allowed users three attempts to type a PIN before confiscating their bank card. This wasobviously no ordinary cash machine.

　　"The number looks right," Langdon confirmed, carefully checking what they had typed andcomparing it to the printout. He motioned to the ENTER key. "Fire away."Sophie extended her index finger toward the keypad, but hesitated, an odd thought now hitting her.

　　"Go ahead," Langdon urged. "Vernet will be back soon.""No." She pulled her hand away. "This isn't the right account number.""Of course it is! Ten digits. What else would it be?""It's too random."Too random? Langdon could not have disagreed more. Every bank advised its customers to choosePINs at random so nobody could guess them. Certainly clients here would be advised to choosetheir account numbers at random.

　　Sophie deleted everything she had just typed in and looked up at Langdon, her gaze self-assured.

　　"It's far too coincidental that this supposedly random account number could be rearranged to formthe Fibonacci sequence."Langdon realized she had a point. Earlier, Sophie had rearranged this account number into theFibonacci sequence. What were the odds of being able to do that?

　　Sophie was at the keypad again, entering a different number, as if from memory. "Moreover, withmy grandfather's love of symbolism and codes, it seems to follow that he would have chosen anaccount number that had meaning to him, something he could easily remember." She finishedtyping the entry and gave a sly smile. "Something that appeared random... but was not." Langdonlooked at the screen.

　　ACCOUNT NUMBER: 1123581321It took him an instant, but when Langdon spotted it, he knew she was right.

　　The Fibonacci sequence.

　　1-1-2-3-5-8-13-21When the Fibonacci sequence was melded into a single ten-digit number, it became virtuallyunrecognizable. Easy to remember, and yet seemingly random. A brilliant ten-digit code thatSaunière would never forget. Furthermore, it perfectly explained why the scrambled numbers onthe Louvre floor could be rearranged to form the famous progression.

　　Sophie reached down and pressed the ENTER key.

　　Noth............