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