In a column with periodic values (e.g., A1 = "1.1", A2 = " ", A3 = "1.2"), I can't find a solution to automate this.

That is, if A1 = "1.1", I want the next cell in that column to be a sequential number. In other words, if I paste whatever formula comes out of this post into A5, where A1 = 1.1 and A2 to A4 = blank, then A5 should = A1+0.1.