Fill Series with a formula/function

[hinomino]

I am not able to find a way to fill a series when the formula contains a functions. Forexample:
=weeknum($A$1)+1
I would like to fill the cells next to this formula by:
=weeknum($A$1)+1
=weeknum($A$1)+2
=weeknum($A$1)+3
=weeknum($A$1)+4
and so on

I have a date in cell A1:
05/05/2009

 

[mikerickson]

How about
=WEEKNUM($A$1)+ROW(A1) , dragged down
or
=WEEKNUM($A$1)+COLUMN(A1) , dragged right