local function phi(n)
  assert(type(n) == 'number', 'n must be a number!')
  local result, i = n, 2
  while i <= n do
    if n % i == 0 then
      while n % i == 0 do n = n // i end
      result = result - (result // i)
    end
    if i == 2 then i = 1 end
    i = i + 2
  end
  if n > 1 then result = result - (result // n) end
  return result
end

local function phi_iter(n)
  assert(type(n) == 'number', 'n must be a number!')
  if n == 2 then
    return phi(n)
  else
    return phi(n) + phi_iter(phi(n))
  end
end

local i, count = 2, 0
while count ~= 20 do
  if i == phi_iter(i) then
    io.write(i, ' ')
    count = count + 1
  end
  i = i + 1
end