Knight's tour

A sequence of moves by which a knight visits every square of a chessboard exactly once. If the final square is one knight's move away from the initial square of the tour, it is referred to as re-entrant.

A tour may have several other interesting properties - for example:

• A symmetric tour is one where the path followed by the knight displays two- or four-way symmetry.
• A magic tour is one where numbering the squares from 1 to 64 in the order visited produces a magic square.

The tour may also be on a board which is not the standard eight-by-eight size; tours on other boards were studied by Euler, among others.

An example of a non-reentrant tour, numbering the squares in visiting order:

22 19 44 37 50 35 46  7 
43 40 23 20 45  6 49 34
18 21 38 41 36 51  8 47
39 42 17 24  5 48 33 52
16  3 62 57 32 53 28  9
61 58 15  4 25 12 31 54
 2 63 60 13 56 29 10 27
59 14  1 64 11 26 55 30

This tour is semimagic, since all rows and columns in the array above sum to 260. A "fully" magic square would also have both diagonals summing to 260. In 2003, it was proven through exhaustive computer analysis that a fully magic tour is impossible on the 8x8 board, while 140 semimagic tours are possible.

Start your knight on the a1 square. Follow the grid row-column.

a1,b3,a5,b7,d8,a7,c8
b6,a8,c7,d5,c3,a4,c5
d7,b8,a6,b4,a2,c1,d3
b2,d1,e3,f5,e7,g8,h6
g4,e5,f7,h8,g6,h4,g2
e1,f3,h2,f1,g3,h1,f2
e4,f6,h5,f4,e2,h1,g2
g5,h7,f8,e5,g7,e8,d6
c4,e2,b1,a3,b5,d4,c2