Puzzle 5 (for the math buff)

[Cracker]

I remember..back in 9^th grade, I gave that problem to my math teacher...drove him fucking nuts, and he finally surrendered.

Because it's random. He made a function table, and there is no pattern of increase/decrease; it is different forwards and backwards (the inverse isn't true). Then he probably checked out the usual sequences and growth patterns (Fibonacci, Pascal's Triangle, primes, triangular, geometric, etc.). Then he said, "fuck it" because he didn't feel like messing with anything Calculus related.