For an integer (b) n 1, let an be the number of ways n tiles can be arranged in a line, from left to right, if the tiles are red, green, or blue, such that no two green tiles are adjacent, and every red tile must have a green tile to its left. Determine a recurrence relation for an as well as enough initial conditions (beginning from n = 1) to uniquely determine your sequence. Make sure to explain how you obtained your recurrence. You do not need to solve the recurrence