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