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