=sum(offset($A$1,0,2*row()-6,1,2))

"Guidu" wrote:

look at cells A3 A4 and A5, I would like to drag and continuing the
serie...jumping two cells while dragging. or like cells D3, E3 and F3
(esentially the same)


A B C D E F

1 2 1 8 2 6 8
2
3 3 (A1+B1) 3 10 14
4 10 (C1+D1) (A1+B1) (C1+D1) (E1+F1)
5 14 (E1+F1)
6