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