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 (1/2)

· tooter · · ·

...
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. (2/2)

SOLUTION TO 304. BACHET'S SQUARE. (1/4)

SOLUTION TO 304. BACHET'S SQUARE. (2/4)

SOLUTION TO 304. BACHET'S SQUARE. (3/4)

SOLUTION TO 304. BACHET'S SQUARE. (4/4)

A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.

Use $and$ for inline LaTeX, and $and$ for display mode.