Coefficient $a_k$ of generating function

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Given a generating function $F(z)$, am I right to say that the coefficient $a_k$ of $[z^n]$ is computed by $\frac{F^{(k)}(0)}{k!}$ $(1)$.

Since we have the definition of $F(z)$ is:

$F(z) = \sum_{i > 0}{a_i*z^i}$

Differentiate $F(z)$ $i$ times then I have $(1)$.

However, do we have any approximation of $a_k$ when $k$ is large, since I don't think compute differentiation of $F(z)$ 100 times is an easy work.

Thanks,