Copy and paste every x number of cells
 

So I think I am stuck and need some help.
I have a list of numbers and want to duplicate a number every so many cells
keeping the duplicate in the list. I have figured out how to insert 2 blank
lines every 20 cells but now need to copy the cell after the blank cells and
paste it into the first blank cell

i.e I have inserted 2 blank cells at A10 and A11 moving the list down, now
I want to copy the contents of cell A132 (the old A10) and paste it in the
blank A10.

I am sure there is an easy way to do this but I am stuck€¦.any help would be
great!

Thanks