How to generate a number sequence in file using vi or Vim?

Question

Is there a way to generate a number sequence in vi or Vim?

For example, for an arbitrary range of lines i  through j (where i < j

Answer 1

:4,8s/^/\=line(".")-3." "    

will do what you want

if you need count=2:

:4,8s/^/\=2*(line(".")-3)." " 

this will give you 2,4,6,8,10

line numbers are hard coded in my example, you could use V to select those lines you want to change.