1, 2, 3, 4,5,6,11,12,13,14,15,16,21,22,23,24,25,26,33,34,35,36,45,46,56,66,55,44,33,22,123,1234,12345,123456,1234561,12345612,123456123,1234561234,123456123456,1234561234561,