Reference to transfer every three rows cell values

[girapas]

In a sheet, and in each of columns AA, AB, AC ... there is, every three rows, the sum of the values of the two above cells. This is repeated in hundreds of rows.

AA AB AC
1 x1 y1 z1
2 x2 y2 z2
3 x1+x2 y1+y2 z1+z2
4 a1 b1 c1
5 a2 b2 c2
6 a1+a2 b1+b2 c1+c2
7
8

I want to transfer all that sums in another area, like this:
AA3 to A1
AB3 to A2
AC3 to A3
AA6 to B1
AB5 to B2
AC6 to B3
etc...

How can I write a reference for the cells AA3, AB3, AC3 ..., in order to use copy for the rest huge number of data?
Thanks in advance

 

[Jerry Sullivan]

Hi girapas,

Enter this formula in A1, then copy down and across the range in A:C
=INDEX(AA:AA,3*ROW()-2,1)