Extensions of the classical transformations of the hypergeometric function F23

It is shown that the classical quadratic and cubic transformation identities satisfied by the hypergeometric function F23 can be extended to include additional parameter pairs, which differ by integers. In the extended identities, which involve hypergeometric functions of arbitrarily high order, the added parameters are nonlinearly constrained: in the quadratic case, they are the negated roots of certain orthogonal polynomials of a discrete argument (dual Hahn and Racah ones). Specializations and applications of the extended identities are given, including an extension of Whipple's identity relating very well poised F67(1) series and balanced F34(1) series, and extensions of other summation identities.