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