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