/prog/ Challenge

Hey, I've stolen this challenge from some website, it's pretty easy but I know most of you will fuck it up.

A sequence is defined by:

n -> n/2 (n is even)
n -> 3n + 1 (n is odd)

Find the longest sequence, with a starting number under one million.

Bonus points when you find the solution for ten million.

>>36
Time-space tradeoff. If I cached the results of earlier calculations it would (often) be quicker to look them up rather than recalculate so many times. But as the bruteforce program took only a minute to run on my PC, I would surely be making unnecessary optimizations.