What is the next number in this sequence?
12, 5, 32, 4, ?
Here are the rules:
I call this the "Twefithritforni" sequence.
Given these rules, it's easy. And any Twefithritforni sequence based on one of those numbers is easy to generate:
5, 32, 4, 9, 12, 5, 32, ...
9, 12, 5, 32, 4, 9, 12, ...
32, 4, 9, 12, 5, 32, 4, ...
This obviously makes a great interview question for a computer-related job. It matches all the major features of other great interview questions:
The one major drawback is that the rules, once you know them, are unambiguous.
You can adjust it to whatever level you're hiring, just adjust the number of numbers given between one and six. You can start with any of the five numbers, and you can even have the missing number in the middle of the given sequence!
If you want a trick question, give a number that's not on the sequence.
Remember, if they haven't recently read a particular post on an obscure blog that maybe gets three hits a year, you don't want them working for you.