Formula for calculating recurring payments?

Hi,

I have an assignment due for a class and I am having alot of difficulty trying to figure this one out.

Say you receive a recurring payment of $1000 a month for 12 months. Each month, you receive another recurring payment for $1000. So in 3 months, you would have received $3000 for the first payment+$2000 for the second payment+$1000 for the third payment. The total would be $6000.

Is there a formula I can use to calculate this easier besides doing it all step by step?