Knight's Tour

An ancient puzzle is the knight's tour, whose goal is to find a path around a chessboard where the knight visits every square in turn without ever going to the same place twice. A more modern take on the same theme is Knight's Tour, formerly known as Numbering Knights, in which a predetermined tour has to be reconstructed.

This is achieved by way of a set of clues to the numbers used in each row and column of the board; 1 is always provided as a starter, with the rows and columns used by cube and square numbers providing further inroads to the puzzle. Other clues take many forms, often including rules that a row must (or must not) contain numbers in a certain range, which are divisible by a given number, which are prime, or which sum to a particular total.

There are some noteworthy aspects to the grid layout; one is that all odd numbers will appear on squares of the same colour, with all even numbers appearing on the opposite colour. Another pivot point is the corner squares; when a number is placed into grid references C2, F2, B3, G3, B6, G6, C7 or F7, it is forced that the nearest corner must contain the next (or previous) number in the sequence.