Insert numbers when column A is blank

[planetpj]

What I am looking to do is get a formula that automatically places numbers in Column A if the cell is blank. Once column A has something in it the numbering stops and when it is blank again start the numbering process starts again from 1.

Book1
	A	B	C	D
1	Barnum
2		1
3		2
4		3
5	Beardsley
6		1
7		2
8		3
9	Blackham
10		1
11		2
12		3
13	BlackRock
14		1
15		2
16		3
17	Bryant
18		1
19		2
20		3
21	Columbus
22		1
23		2
24		3
Sheet1

 

[Juan Pablo González]

Something like this ?

Libro3
	A	B	C	D
1	Barnum
2		1	1
3		2	2
4		3	3
5	Beardsley
6		1	1
7		2	2
8		3	3
9	Blackham
10		1	1
11		2	2
12		3	3
13	BlackRock
14		1	1
15		2	2
16		3	3
17	Bryant
18		1	1
19		2	2
20		3	3
21	Columbus
22		1	1
23		2	2
24		3	3
Hoja1

 

[planetpj]

Juan you got it right on the ball. Buy the way a very interesting answer!! I was trying to go about it differently but you learn something new everyday!!! Thank you again and God Bless!!