X ( 1 , 6 , 2 , 7 ) X ( 3 , 9 , 4 , 8 ) X ( 5 , 15 , 6 , 14 ) X ( 7 , 18 , 8 , 19 ) X ( 9 , 17 , 10 , 16 ) X ( 11 , 5 , 12 , 4 ) X ( 12 , 20 , 13 , 19 ) X ( 15 , 11 , 16 , 10 ) X ( 17 , 3 , 18 , 2 ) X ( 20 , 14 , 1 , 13 ) {\displaystyle X(1,6,2,7)X(3,9,4,8)X(5,15,6,14)X(7,18,8,19)X(9,17,10,16)X(11,5,12,4)X(12,20,13,19)X(15,11,16,10)X(17,3,18,2)X(20,14,1,13)}
