304.--BACHET'S SQUARE.

One of the oldest card puzzles is by Claude Caspar Bachet de Méziriac,

first published, I believe, in the 1624 edition of his work. Rearrange

the sixteen court cards (including the aces) in a square so that in no

row of four cards, horizontal, vertical, or diagonal, shall be found two

cards of the same suit or the same value. This in itself is easy enough,

but a point of the puzzle is to find in how many different ways this may

be done. The eminent French mathematician A. Labosne, in his modern

edition of Bachet, gives the answer incorrectly. And yet the puzzle is

really quite easy. Any arrangement produces seven more by turning the

square round and reflecting it in a mirror. These are counted as

different by Bachet.

Note "row of four cards," so that the only diagonals we have here to

consider are the two long ones.

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