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