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