2, 3, 10, 12, 13, 20, 21, 22 and so on up to 38, 39, __

I was staring at those numbers for ages trting to work it and then it just dawned on me.

The answer is 200.

Two, Three, Ten, Thirteen, Twenty.......Thirty Nine, Two hundred
The squence of numbers that when spelt out begin with the letter T.