Numbers always INDIRECT same cell from previous sheet

How to reference to always indirect the same cell for the previos sheet?

example sheet 1, sheet 2, sheet3...

sheet 2 c3=sheet 1 a1 + sheet 2 a2

sheet 3 c3=sheet 2 a1 + sheet 3 a2

sheet 4 c3=sheet 3 a1 + sheet 4 a2

and so on as a formula could copy to the next sheet # c3 maintaining the same, thanks