Starting from the top of a deck of cards, each card is pushed over so that it just balances. The overhang for each card is half the corresponding entry in the harmonic sequence and the total overhang is given by half the partial sum of the harmonic series.
J. Derbyshire, Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics, Washington, DC: Joseph Henry Press, 2003 pp. 3–9.
Wolfram Demonstrations Project
Published: March 7 2011