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