I suppose most applicants to Google should have some idea about this?  I know what a Fibonacci sequence IS, but I wouldn't think of it.  
I would have said, "I'm going to assume that n is 1."
The other questions on there are more absurd.  I was originally going to say absurdist, but that would imply that the people who wrote them were in on the joke.
A friend of mine's response was, "you know, a hiring committee spent a loooong time coming up with these questions."  
Groupthink is painful!