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