X ( 1 , 4 , 2 , 5 ) X ( 3 , 9 , 4 , 8 ) X ( 5 , 10 , 6 , 11 ) X ( 7 , 15 , 8 , 14 ) X ( 9 , 3 , 10 , 2 ) X ( 11 , 18 , 12 , 1 ) X ( 13 , 16 , 14 , 17 ) X ( 15 , 7 , 16 , 6 ) X ( 17 , 12 , 18 , 13 ) {\displaystyle X(1,4,2,5)X(3,9,4,8)X(5,10,6,11)X(7,15,8,14)X(9,3,10,2)X(11,18,12,1)X(13,16,14,17)X(15,7,16,6)X(17,12,18,13)}
