I don't think he is talking about the closed form expression (at least I know what a closed-form is and still couldn't understand the question).
There was no information whatsoever about what changes on each iteration... if nothing changes then the answer would be a constant of whatever rabbits were at the beginning... and that doesn't sound about right :/
Re:My Startup Job Interview
by agibsonccc on Thursday September 19, 2013 @10:53AM
(#6411980)
Bah got ya.
A closed form expression is basically just a mathematical function used to model a potentially infinite series.
Take a look here: http://en.wikipedia.org/wiki/Closed-form_expression
Look at the first and second examples.
You'll see the big summation sign (for loop: i to infinite) and then an explicit function.
If you want to think, what the heck is this math crap used for: think about a more basic everyday concept like recursion. How do you know it will terminate?