[0,2,1,4,3,6,5,9,7,8,11,10,13,12,15,16,14,18,17,20,19,22,21,24,23,26,25,28,27,30,29,32,31,34,33,36,35,38,37,40,39,42,41,44,43,46,45,48,47,50,49,52,51,54,53,56,55,58,57,60,59,62,61,64,63,66,65,68]