In order to show this, I first showed the video below. which does an excellent job of explaining the method of developing an explicit pattern rule and the reasoning behind the formula.
While this video is excellent for explaining everything, students sometimes have difficulty remembering all the steps, so I created a shorter version that may help students to create an explicit pattern rule. The key is to remember that they need to multiply by one less than the term number we are looking for. Here is the educreation: