Sum of series 14/(7n-3)(7n+4)

Given number:
$$\frac{14}{7 n - 3} \left(7 n + 4\right)$$
It is a series of species
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
In this case
$$a_{n} = \frac{14 \left(7 n + 4\right)}{7 n - 3}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{\left(7 n + 4\right)^{2} \left|{\frac{1}{7 n - 3}}\right|}{7 n + 11}\right)$$
Let's take the limit
we find

True

False