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