> Is there any way to make this program check if there
> are more directories in a series? For example, If
> there's a directory called www.website.com/1/ is it
> possible to have it check for /2/ and up?
Most sites will not give a directory listing for /1/
If it does the httrack can spider up/down the listing.

You can also specify a list: 
Number sequences: How to mirror only files/URLs using a certain ID/number
range - <http://httrack.kauler.com/help/URL_number_sequences>