Here is the problem as Euler stated it:
"Thirty-six officers of six different ranks and drawn from six different regiments were to be arranged in a square so that each horizontal and vertical line contained six officers, all of different ranks and different regiments."
An idea destined to become a classic
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Euler then began studying what he would call Graeco-Latin squares. A Latin square of order n is a square of n2 cells filled with the first n letters of the Latin alphabet, such that the letters in every row and column are all distinct.
