Ok, this was a kinda funny. In Puzzle Agent 2, I got to the puzzle "Digits in Space", I needed the hints and I figured out that it was the sequence for pi. The only problem was, I didn't know what numbers where next in the sequence.
But, then I remembered someone who did...MAX! So, I popped in the 1st season of "Sam & Max: Save the World". I started up Episode 4: Abe Lincoln Must Die, and just clicked on the pay phone. (I had to reload a few times, just to make sure I go the number right.) Sure enought, I tried the number and it was right!
Wow, Telltale actually hid a clue for one of their current games, in one of their previous games...Genius.