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