Counting consecutive blank cells

I would like to be able to find the LONGEST consecutive sequence of blank cells in a
column. The following example would have to return 3.

A1:17
A2:
A3:
A4:12
A5:
A6:10
A7:14
A8:
A9:
A10:
A11:8
A12:6

many thanks,
Kevin

I did not find a way to put it in only one formula what i came up with is this:

A1 3
A2 17 0
A3 1
A4 2
A5 12 0
A6 1
A7 10 0
A8 14 0
A9 1
A10 2
A11 3
A12 8 0
A13 6 0

A1 =MAX(B2:B14)
A2 17 =SI(A2="",1 + B1,0)
A3 =SI(A3="",1 + B2,0)
A4 =SI(A4="",1 + B3,0)
A5 12 =SI(A5="",1 + B4,0)
A6 =SI(A6="",1 + B5,0)
A7 10 =SI(A7="",1 + B6,0)
A8 14 =SI(A8="",1 + B7,0)
A9 =SI(A9="",1 + B8,0)
A10 =SI(A10="",1 + B9,0)
A11 =SI(A11="",1 + B10,0)
A12 8 =SI(A12="",1 + B11,0)
A13 6 =SI(A13="",1 + B12,0)