Fill Help!

I'm having trouble autofilling cells. I have a column of cells that contain the averages for a neighboring column values but I am having trouble auto-filling the remaining cells with the progressing formula. In the example below, I would like column C to be auto filled with the remaining formulas in sequence with the pattern I've already started. Is this possible? >_<

A B C
1 1 =average(a1:a2)
2 3 =average(a3:a4)
3 5 =average(a5:a6)
4 7
5 9
6 11
7 13
8 15

Thank you for your time!

That didn't work unfortunately, but thank you for your help :D

I'm really just trying to auto fill the cells not past a formula to one specific cell.

Got it! Thanks for all your help!