excel - Drag formula and have it reference every other cell -

i have simple if statement made works. however, when try drag formula automatically populates other cells, doesn't reference correct cells. because increments reference cell chronologically (i.e: goes x y z) need increment every other cell (i.e: x z ab) how that?

here snippet of place formula is:

here snippet of want reference:

you can x3, z3, ab3 etc filling following right.

=index($x:$cp, row(3:3), (column(a:a)-1)*2+1) 

this makes formula in cq3,

=if(index($x:$cp, row(3:3), (column(a:a)-1)*2+1)>1, 2, if(index($x:$cp, row(3:3), (column(a:a)-1)*2+1)=1, 1, 0)) 

fill down row 4.