Drag a formula that references a cell from another Sheet (Skipping a cell incrementing 1)

Hi, I have a formula in Sheet2 A1 ='Sheet1!A1
On Sheet2 A2 I have =A1 in the cell

When I drag this down in Sheet2 I need every other cell to increase by one so that I get this output

A1 = SDI[1] "COMES FROM SHEET 1 CELL A1"
A2 = SDI[1] = A1
A3 = SDI[2] "COMES FROM SHEET 1 CELL A2"
A4 = SDI[2] = A3

AND SO ON

This is the output I am currently getting

A1 = SDI[1] "COMES FROM SHEET 1 CELL A1"
A2 = SDI[1] = A1
A3 = SDI[3] "COMES FROM SHEET 1 CELL A3"
A4 = SDI[3] = A3




Is this possible, i am racking my brain.

Thanks for responding. I played with the formula, and i still cant get it to work. I'll try and explain this a little better. I have a cell on Sheet2 (F3), this cell references a cell on Sheet1, (B2) with the Text "SDI[0]". On sheet two in cell (F4) i have the formula =(F3). I then highlight Cells F3 and F4 and drag down.

So on Sheet1 in collum B i have:
B2 - SDI[0]
B3 - SDI[1]
B4 - SDI[3]
ect

Sheet2
F3 Formula is =Sheet1 B2 wich is SDI[0]
F4 formula is =F3 wich is SDI[0]

So when i Drag cell F3 and F4 down cells F5 and F6 should be:
F5 = SDI[1]
F6 = SDI[1]

ect

Thanks a million, you just saved me days of work.

I would Like to add one more tweak to this formula, how would I edit the following formula to not return a 0 if the cell I am referenceing is blank

=INDEX('HAS-LAW SDI'!C:C,INT((ROWS($F$3:$F4)+1)/2)+1)

Thanks, that did the trick!