Q:

generate non duplicate integers in Lua

I am trying to generate 5 random non duplicate values between 0,500 and assign them to 5 variables using Lua.
So far I have used the following code which unsuccessfully attempts to generate the random numbers and assigns the values. The problem is:

this code is sometime generating the duplicate numbers
the name which I want to look like x-1, x-2 and so on, prints like x-1, x-12.

Can you please help me with this.
Example:
v_Name = "x-"
for i =1, 5 do
  X = math.random (0, 500)
  v_Name = v_Name..(i)
  print (v_Name)
  print (X)
 end 

A:

Here is a solution, clarified in the comments:
math.randomseed( os.time() ) -- first, sets a seed for the pseudo-random generator

local  function my_random (t,from, to)  -- second, exclude duplicates
   local num = math.random (from, to)
   if t[num] then  num = my_random (t, from, to)   end
   t[num]=num 
   return num
end

local t = {}    -- initialize  table with not duplicate values
local Name = "x-"
for i =1, 5 do
  X = my_random (t, 0, 500)
  v_Name = Name .. i    -- oh, may be use a table?
  print (v_Name, "=" ,X)
 end 

