Hipparchus and the 2000 Year-Old Clue

In 1870, Ernst Schroeder revealed the concept of Schröder numbers – his latest discovery. Nobody realized that two thousand years earlier, the greatest of ancient astronomers, Hipparchus, was already using these numbers. It took more than another century until a puzzling declaration by Plutarch was explained by David Hough, revealing an undreamed-of development in Ancient Greek mathematics.

This is a story of Ancient Greek rivalries, which left only a solitary, perplexing clue to the advanced state of combinatorics in that era, and how the clue was finally recognized and understood.