Symmetries of Coefficients of Three-Term Relations for the   Hypergeometric Series
  Any three hypergeometric series whose respective parameters, a, b and c, differ by integers satisfy a linear relation with coefficients that are rational functions of a, b, c and the variable x. These relations are called three-term relations. This paper shows that the coefficients of three-term relations have properties called symmetries, and gives explicit formulas describing the symmetries. 
Yuka Yamaguchi
math.RT