DouKaku?

math.randomseed(os.time())

function iota(n)
  local t = {}
  for i=1,n do
    table.insert(t, i)
  end
  return t
end

function lot(m, n)
  function pick(winners, rest, m)
    if m == 0 then
      return winners
    else
      local picked = table.remove(rest, math.random(#rest))
      table.insert(winners, picked)
      return pick(winners, rest, m-1)
    end
  end
  return pick({}, iota(n), m)
end

function show_array(t)
  print("["..table.concat(t, " ").."]")
end

show_array(lot(arg[1], arg[2]))