Error when sequencing auto number

I thought there was a much simpler way to generate a column of sequential numbers. In its simplest form, I start with 1,2. in a1 and a2; then put cursor at the bottom right cell 2, the cursor changes to a cross and then just drag the cell as long as I need, e.g., down ten cells creating 3,4,5,6,7,8,9,10,11,12. All I get now is a column of 1's. I had to create formula in a2, a1+1. then copy down to a12, then copy and paste the entire column as value in order to get a column of reference rows. Pretty absurd.