\[F\left({a,1-a\atop c};z\right)=(1-2z)^{1-a-c}(1-z)^{c-1}F\left({\frac{1}{2}(a+%
c),\frac{1}{2}(a+c-1)\atop c};\frac{4z(z-1)}{(1-2z)^{2}}\right),\]