This is a repost from MSE as I haven’t got anything so far there.

Ramanujan gave the following series evaluation $ $ 1+9\left(\frac{1}{4}\right)^{4}+17\left(\frac{1\cdot 5}{4\cdot 8}\right)^{4}+25\left(\frac{1\cdot 5\cdot 9}{4\cdot 8\cdot 12}\right)^{4}+\cdots=\dfrac{2\sqrt{2}}{\sqrt{\pi}\Gamma^{2}\left(\dfrac{3}{4}\right)}$ $ in his first and famous letter to G H Hardy. The form of the series is similar to his famous series for $ 1/\pi$ and hence a similar approach might work to establish the above evaluation. Thus if $ $ f(x) =1+\sum_{n=1}^{\infty}\left(\frac{1\cdot 5\cdots (4n-3)}{4\cdot 8\cdots (4n)}\right)^{4}x^{n}$ $ then Ramanujan’s series is equal to $ f(1)+8f'(1)$ . Unfortunately the series for $ f(x) $ does not appear to be directly related to elliptic integrals or amenable to Clausen’s formula used in the proofs for his series for $ 1/\pi$ .

Is there any way to proceed with my approach? Any other approaches based on hypergeometric functions and their transformation are also welcome. Any reference which deals with this and similar series would also be helpful.