Emacs: Consecutive numbers / digits in a rectangle column / vertically

In Emacs 24.1, there’s a command

  C-x r N (‘M-x rectangle-number-lines’)

for numbering lines.

Mark a vertical strip of 1 char wide rectangle, e.g. with
  C-SPC-arrowKeyDown
and press
  C-x r N
That's it.

If you want to start from another number than 1, e.g. 12, use the **C-u** prefix, e.g.

  C-u C-x r N 12 RET RET

Using the C-u prefix it is also possible to change the format of the numbers, e.g. to
01
02
03
04