Do you know what a Knight’s Tour is?” he added, seeing my confusion. I shook my head in the negative. “It’s a mathematical puzzle. You move the Knight to every square of the chessboard without landing on the same square twice, using regular Knight moves: two squares horizontal and one vertical or the reverse. Through the ages, mathematicians have tried to come up with formulas to do it. Euler had a new one. So did Benjamin Franklin. A Closed Tour would be one in which you wound up on the same square you started from.”
