calculation puzzle - A sequence defined by a single fraction

I have a sequence of numbers here, which follow a very simple rule that can be expressed using a single fraction:

1, 2, 10, 11, 13, 15, 20, 22, 25, 28, ...

What is this rule (in particular, what is the fraction), and what are the next few numbers in the sequence?

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Since nobody's gotten it yet, I'll add a few hints over the next little while.

(06-16 13:22) 1. The numbers in the sequence never get more than 2 digits long.

Answer

The items in the sequence should be numbered from 2 onwards, and then item $b$ is

the base-$b$ representation of $\displaystyle \left \lfloor \frac{b^2}{4} \right \rfloor$, which can also be written as just $\displaystyle \left \lfloor \frac{100}{4} \right \rfloor$, since $b$ in base $b$ is always $10$.

So the fraction that defines the sequence is

100/4

and the next few entries in the sequence are:

30, 33, 37, 3B, 40, 44, 49, 4E, 50.