It began as no more than a puzzle posed on the sidelines of the 1977 International Mathematical Olympiad, held that year in Belgrade, Yugoslavia. But its origins may go back further. Here is the problem as it was posed:
1,
11,
21,
1211,
The audioactive sequence
Self-describing sequences are fairly well known among mathematics enthusiasts, but their history often is not. Even less familiar, no doubt, is the work of the man who helped bring them into the mathematical mainstream: John Conway, who devoted his life to having fun with mathematics.
