To quickly find the formula for any geometric sequence, just follow these easy steps:

1. Find the first term ($a_1$): This is the starting number in the sequence.

2. Figure out the common ratio ($r$): You can get this by dividing any term by the term that comes before it. For example, you can find $r$ like this: $r = \frac{a_2}{a_1}$.

3. Use the explicit formula: The formula looks like this:
   $a_n = a_1 \cdot r^{(n - 1)}$
   Here, $n$ is just the number of the term you want.

Example:

If your sequence starts with $3$ (so $a_1 = 3$) and the common ratio is $2$ (meaning $r = 2$), the formula you would use is
$a_n = 3 \cdot 2^{(n - 1)}.$

This lets you find any term in the sequence!