Find the common ratio or common difference.

Let's check the ratio between consecutive terms:
$\frac{6}{2} = 3$
$\frac{18}{6} = 3$
$\frac{54}{18} = 3$
Since there is a constant ratio, this is a geometric series.

The first term is $a = 2$.
The common ratio is $r = 3$.

The formula for the $n^{th}$ term ($T_n$) of a geometric series is:

A) $T_n = 2(3)^{(n-1)}$
B) $T_n = 2(4)^{(n-1)}$
C) $T_n = 2(1)^{(n-1)}$
D) $T_n = 2(3)^{(n+1)}$

The derived formula matches option A.

The final answer is $\boxed{\text{A}}$.