Answer:
Recursive: 

Explicit: 

Explanation:
First, note that this is a geometric sequence. This is because each term is 2 times its previous term. 
The standard recursive form for a geometric sequence is: 

Where n is the nth term, so n-1 is the previous term, and r is the common ratio. 
Substitute 2 for r. 
Therefore, our recursive formula is: 

The standard form of the explicit formula for geometric sequences is: 

Again, r is the common ratio and a is the initial term. 
The common ratio is 2 and the initial term is 2. So, substitute: 

And that's our explicit formula. 
And we're done!