A Classic Proof of a Recurrence for a Very Classical Sequence
  By practicing the philosophy of our beloved late master, Marco Schutzenberger, to whose memory this article is dedicated, we give an insightful bijective proof of the three-term recurrence satisfied by the Hipparchus-Schroeder numbers 1,1,3,11,45,197,903, ... 
Dominique Foata (Strasbourg) and Doron Zeilberger (Temple Univ.)