What does it mean to be ``random''? What matters to most of these problems is that there is a sequence of numbers with no observable patterns. One could generate such a sequence by looking at radioactive decay or something, but on a computer one usually generates a new random number from the old one (no randomness at all!) One starts these random number generators with a seed: if you don't change the seed, you get exactly the same random numbers every time!
Statistical Mechanics: Entropy, Order Parameters, and Complexity, now available at Oxford University Press (USA, Europe).