External Edges Patterning Solution

1. The class of problems.

   How many external edges on a "line of squares"
   of length n?

2. Identifying several of the simplest problem.

   I1 = How many external edges on a 1x1 line?
   I2 = How many external edges on a 1x2 line?
   I3 = How many external edges on a 1x3 line?
   I4 = How many external edges on a 1x4 line?
   

3. Solving the several simplest instances.

   Solution(I1) = 4
   Solution(I2) = 6
   Solution(I3) = 8
   Solution(I4) = 10
   

4. Observing a pattern relating the instances to
   their solutions, and stating the pattern as a solution
   to the generic problem associated with the problem
   class.

   The number of external edges on a "line of squares"
   of length n is ( ( n * 2 ) + 2 ).