TITLE: Evaluating a series of hypergeometric functions
QUESTION [7 upvotes]: I would like to prove (or disprove) the following statement:
$$
\sum_{n=0}^\infty \left[\frac{{}_2{\rm F}_1\left(\frac{1}{2},\frac{1-n}{2};\frac{3}{2};1\right)}{n!}\right] = \frac{\pi}{2} \left[ \sum_{a=0}^\infty \frac{1}{4^a (a!)^2} + \frac{1}{2} \sum_{b=0}^\infty \frac{\left(\frac{1}{2}\right)^{2b}}{\Gamma\left(b+\frac{3}{2}\right)^2}\right]
$$
also can be seen as
$$
\sum_{n=0}^\infty \left[\frac{{}_2{\rm F}_1\left(\frac{1}{2},\frac{1-n}{2};\frac{3}{2};1\right)}{n!}\right] = \frac{\pi}{2} \bigg[ I_0(1) + L_0(1) \bigg]
$$
Where $I_0(1)$ is the modified bessel function of the first kind and $L_0(1)$ is the modified struve function.
Major brownie points on the line here!

REPLY [2 votes]: Semiclassical has told me to post an answer to my own question using the technique i have explained to him, now for me to go any further i should state that the original function i am dealing with is:
$
{}_2F_1(\frac{1}{2}, \frac{1-n}{2}; \frac{3}{2};\cos^2 (x))
$ 
 therefore using the power series of a hyper geometric function i can say:
$$
{}_2F_1(\frac{1}{2}, \frac{1-n}{2}; \frac{3}{2};\cos^2 (x)) = \sum_{a=0}^{\infty} \frac{(\frac{1}{2})_a (\frac{1-n}{2})_a \cos^{2a}(x)}{(\frac{3}{2})_a a!}
$$
Having $(f(x))_a be the rising factorial therefore with the definition of a rising factorial  as using gamma functions i can state the following aswell:
$$
{}_2F_1(\frac{1}{2}, \frac{1-n}{2}; \frac{3}{2};\cos^2 (x)) =  \sum_{a=0}^{\infty} \frac{\Gamma(\frac{1}{2}+a) \Gamma(\frac{1-n}{2}+a) \Gamma(\frac{3}{2}) \cos^{2a}(x)}{\Gamma(\frac{3}{2}+a)\Gamma(\frac{1}{2}) \Gamma(\frac{1-n}{2}) a!}
$$
using the following identities i can simplify the function more
$\Gamma(\frac{1}{2}) = \sqrt{\pi}$
$\Gamma(\frac{3}{2}) = \sqrt{\pi}/2$
$ \Gamma(\frac{1}{2} + n) = \frac{(2n)! \sqrt{\pi}}{4^{n} n!}$
$$
{}_2F_1(\frac{1}{2}, \frac{1-n}{2}; \frac{3}{2};\cos^2 (x)) =  \frac{1}{2}\sum_{a=0}^{\infty}\frac{\pi(2a)!4^{a+1}(a+1)! \Gamma(\frac{1-n}{2}+a)}{ \pi 4^{a}(a!)^2 (2a+2)!  \Gamma(\frac{1-n}{2})}
$$
$$
=  \frac{1}{2}\sum_{a=0}^{\infty}\frac{4 \cos^{2a}(x) (a+1) \Gamma(\frac{1-n}{2}+a)}{ a!(2a+2)(2a+1) \Gamma(\frac{1-n}{2})}
$$
$$
=  \frac{4}{2}\sum_{a=0}^{\infty}\frac{\cos^{2a}(x) \Gamma(\frac{1-n}{2}+a)}{ 2 a!(2a+1) \Gamma(\frac{1-n}{2})}
$$
$$
= \sum_{a=0}^{\infty}\frac{\cos^{2a}(x)\Gamma(\frac{1-n}{2}+a)}{ a!(2a+1) \Gamma(\frac{1-n}{2})}
$$
Which i know looks very ugly, but when i graphed  this on Mathematica on the interval $ [0,2\pi]$ it was the same result as the function given by Semiclassical (in my specific scenario). therefore you can say that they are equal i suppose?