Interview Question, What do they want to accomplish?

First the answer: 116 - it's the decimal form of the ASCII letters "this is correc" so the letter 't' comes next.

But, while I figured out (given your clues) the pattern, I'd make a few comments:

• Presumably he was trying to see how you attacked a difficult, even nebulous problem.
• If he truly sat silent for 5 minutes at a time, then he needs to work on his interviewing style, if only to encourage you to talk.

That said:

• Did you think out loud and talk through the various approaches you used?
• Did you ask probing questions about the problem domain?

Incidentally, I mis-remembered 'a' as 96 rather than 97, so I would have missed the problem. But I would have been talking the entire time.

You have to convey your thought processes and not just come up with an answer. I've twice had interviewers give me problems that they didn't expect me to solve, both with the intent of seeing my approach to solving them.

(Incidentally, I got offers from both interviews, because I talked my way through the problems - even though I couldn't finish solving them.)

Anyone who writes down ascii values in decimal is insane. The sequence would look a lot more familiar if it were in hex.

Your question reminded me of an ad campaign of EA some years ago: