Tenemos la indeterminación de tipo
oo/oo,
tal que el límite para el numerador es
$$\lim_{n \to \infty}\left(\frac{\left(5^{n} + 1\right) n!^{2} \left(2 \left(n + 1\right)\right)!}{\left(2 n\right)! \left(n + 1\right)!^{2}}\right) = \infty$$
y el límite para el denominador es
$$\lim_{n \to \infty}\left(5 \cdot 5^{n} + 1\right) = \infty$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{n \to \infty}\left(\frac{\left(5^{n} + 1\right) n!^{2} \left(2 n + 2\right)!}{\left(5 \cdot 5^{n} + 1\right) \left(2 n\right)! \left(n + 1\right)!^{2}}\right)$$
=
Introducimos una pequeña modificación de la función bajo el signo del límite
$$\lim_{n \to \infty}\left(\frac{\left(5^{n} + 1\right) n!^{2} \left(2 \left(n + 1\right)\right)!}{\left(5 \cdot 5^{n} + 1\right) \left(2 n\right)! \left(n + 1\right)!^{2}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\frac{d}{d n} \frac{\left(5^{n} + 1\right) n!^{2} \left(2 \left(n + 1\right)\right)!}{\left(2 n\right)! \left(n + 1\right)!^{2}}}{\frac{d}{d n} \left(5 \cdot 5^{n} + 1\right)}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{5^{- n} \left(\frac{5^{n} \log{\left(5 \right)} n!^{2} \left(2 n + 2\right)!}{\left(2 n\right)! \left(n + 1\right)!^{2}} + \frac{2 \cdot 5^{n} n!^{2} \Gamma\left(2 n + 3\right) \operatorname{polygamma}{\left(0,2 n + 3 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}} - \frac{2 \cdot 5^{n} n!^{2} \left(2 n + 2\right)! \Gamma\left(n + 2\right) \operatorname{polygamma}{\left(0,n + 2 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{3}} - \frac{2 \cdot 5^{n} n!^{2} \left(2 n + 2\right)! \Gamma\left(2 n + 1\right) \operatorname{polygamma}{\left(0,2 n + 1 \right)}}{\left(2 n\right)!^{2} \left(n + 1\right)!^{2}} + \frac{2 \cdot 5^{n} n! \left(2 n + 2\right)! \Gamma\left(n + 1\right) \operatorname{polygamma}{\left(0,n + 1 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}} + \frac{2 n!^{2} \Gamma\left(2 n + 3\right) \operatorname{polygamma}{\left(0,2 n + 3 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}} - \frac{2 n!^{2} \left(2 n + 2\right)! \Gamma\left(n + 2\right) \operatorname{polygamma}{\left(0,n + 2 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{3}} - \frac{2 n!^{2} \left(2 n + 2\right)! \Gamma\left(2 n + 1\right) \operatorname{polygamma}{\left(0,2 n + 1 \right)}}{\left(2 n\right)!^{2} \left(n + 1\right)!^{2}} + \frac{2 n! \left(2 n + 2\right)! \Gamma\left(n + 1\right) \operatorname{polygamma}{\left(0,n + 1 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}}\right)}{5 \log{\left(5 \right)}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{5^{- n} \left(\frac{5^{n} \log{\left(5 \right)} n!^{2} \left(2 n + 2\right)!}{\left(2 n\right)! \left(n + 1\right)!^{2}} + \frac{2 \cdot 5^{n} n!^{2} \Gamma\left(2 n + 3\right) \operatorname{polygamma}{\left(0,2 n + 3 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}} - \frac{2 \cdot 5^{n} n!^{2} \left(2 n + 2\right)! \Gamma\left(n + 2\right) \operatorname{polygamma}{\left(0,n + 2 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{3}} - \frac{2 \cdot 5^{n} n!^{2} \left(2 n + 2\right)! \Gamma\left(2 n + 1\right) \operatorname{polygamma}{\left(0,2 n + 1 \right)}}{\left(2 n\right)!^{2} \left(n + 1\right)!^{2}} + \frac{2 \cdot 5^{n} n! \left(2 n + 2\right)! \Gamma\left(n + 1\right) \operatorname{polygamma}{\left(0,n + 1 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}} + \frac{2 n!^{2} \Gamma\left(2 n + 3\right) \operatorname{polygamma}{\left(0,2 n + 3 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}} - \frac{2 n!^{2} \left(2 n + 2\right)! \Gamma\left(n + 2\right) \operatorname{polygamma}{\left(0,n + 2 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{3}} - \frac{2 n!^{2} \left(2 n + 2\right)! \Gamma\left(2 n + 1\right) \operatorname{polygamma}{\left(0,2 n + 1 \right)}}{\left(2 n\right)!^{2} \left(n + 1\right)!^{2}} + \frac{2 n! \left(2 n + 2\right)! \Gamma\left(n + 1\right) \operatorname{polygamma}{\left(0,n + 1 \right)}}{\left(2 n\right)! \left(n + 1\right)!^{2}}\right)}{5 \log{\left(5 \right)}}\right)$$
=
$$\frac{4}{5}$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 1 vez (veces)