1975, Gregory Chaitin, "Randomness and Mathematical Proof", Scientific American, (232), May 1975, pp. 47–52, reprinted in Information, Randomness & Incompleteness: Papers on Algorithmic Information Theory Tossing a coin is a classical procedure for producing a random number .... Tossing a coin 20 times can produce any one of 2²⁰ ... binary series, and each of them has exactly the same probability.
Source: wiktionary