RC[-1] Formula: Calculates Monthly Residuals

I'm trying to make a worksheet that calculates monthly residuals. For example, if I have income of $275 in the first month and then the next month I have the first $275 and an additional $275, and so on. I've created the following formula

=RC[-1]+(RC[-1]*2)+(RC[-1]*3)+(RC[-1]*4)+(RC[-1]*5)+(RC[-1]*6)+(RC[-1]*7)+(RC[-1]*8)+(RC[-1]*9)+(RC[-1]*10)+(RC[-1]*11)+(RC[-1]*12)

where RC[-1] is the base amount that adds on every month. This gives me the number I am looking for. However, I am wondering if there is an easier way to do this.