Thanks for the reply! To clarify, this is simply a personal endeavor that I've taken to developing formulas. Below is a link to the spreadsheet I've used as a way to check any formula written.
Beginning on the second
page, you'll see weeks with corresponding numbers below. Each number highlighted in below is considered "new" sales. Looking further, you'll see each figure repeats every four weeks. This is done over and over until 48 weeks is reached. From there, you can see that the amount is totaled. That totaled amount is the end figure.
As a starting point, the formula I've put together is as follows:
Of course, I assumed there is a simpler way to word this. I also cannot explain why the number being multiplied against (12,11,10) have to decrease. I know this is a complete cluster, but any help or direction you can give is greatly appreciated