Defaults

   o  If you omit n from either .LIST or .END LIST, you get the
      .SKIP value associated with .PARAGRAPH or .SET PARAGRAPH or 1
      (if you have not specified such a value).

   o  If you omit "x," you get a sequence of decimal numbers
      beginning with 1, or you get another kind of sequence if you
      enter the .DISPLAY ELEMENTS command after the .LIST.