they way the puzzle is described in the article i really dont get whats the problem of a 6x6. especially after looking at the chess board 5x5. assume every number represents a different chess figure:

    1 2 3 4 5 6    21
    2 3 1 5 6 4    21
    3 1 2 6 4 5    21
    4 5 6 1 2 3    21
    5 6 4 2 3 1    21
    6 4 5 3 1 2    21

   212121212121