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