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