Eggs inc problem

So I play eggs inc, an idle game where you have chickens that lay eggs. However, every minute, we receive more chickens that also lay eggs to sell. If I wanted to calculate how many eggs will be laid in an hour and put it in google sheets, how would I go about doing that?

For example, let's say I started with 10 chickens. Each chicken lays 1 egg per minute. I gain 2 chickens each minute. This means that after 5 minutes, I would lay 70 eggs (10+12+14+16 + 18). I understand that I need to make some kind of series and a formula that finds the sum.

Could I have some help with this? If anyone is familiar with google sheets, implication of this formula would also be helpful. Thank you!!

(I just graduated high school in honors if that information is useful)