Answer:
Explicit formula: 
Step-by-step explanation:
Let the number of squares in
layer be 
Given:
Number of squares in first layer, 
Number of squares in second layer, 
Therefore, the number of squares increases by a factor of 2.
So, it follows a geometric sequence with the first term as 6 and common ratio of 2.
For a geometric sequence, the
term with common ratio
is given as:

Here, 
∴ Explicit formula: 