28. [14] Johnny the grad student is typing all the integers from 1 to $\infty$, in order. The 2 on his computer is broken however, so he just skips any number with a 2. What's the 2008th number he types?
Answer: 3781 Write 2008 in base 9 as 2671 , and interpret the result as a base 10 number such that the base 9 digits $2,3, \ldots 8$ correspond to the base 10 digits $3,4, \ldots 9$. This gives an answer of 3781 .