PUZZLE: What characterizes this (infinite) sequence, the first few terms of which are as follows:

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 17, 18, 20, 23, 25, 26, 28, 29, 32, 33, 38, 39, 41, 43, 46, 48, 50, ...

?

(Perhaps it's better to describe this as a subset of the positive integers which has been put in ascending order.)

--Dan