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