We have indeterminateness of type
oo/oo,
i.e. limit for the numerator is
$$\lim_{n \to \infty}\left(2 \cdot 2^{n}\right) = \infty$$
and limit for the denominator is
$$\lim_{n \to \infty} 2^{n} = \infty$$
Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
$$\lim_{n \to \infty}\left(2^{- n} 2^{n + 1}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\frac{d}{d n} 2 \cdot 2^{n}}{\frac{d}{d n} 2^{n}}\right)$$
=
$$\lim_{n \to \infty} 2$$
=
$$\lim_{n \to \infty} 2$$
=
$$2$$
It can be seen that we have applied Lopital's rule (we have taken derivatives with respect to the numerator and denominator) 1 time(s)