Filling Merged Cells

[PITA]

Col. A [ and only A] has every 3 rows merged.

I would like to insert an item number in every set of
3 rows e.g. cells A1:A3 = *1*; A4:A6 = *2* etc.

Usually I would use Edit/Fill Columns etc. but with no success.
Any ideas plse.

TIA
Bill

 

[Max]

Select A1:A6
(i.e. the first 2 merged cells with "1" and "2" entered)

Copy down per as normal
(i.e. drag down the fill handle "+" at the bottom right corner)