The Collatz conjecture.

collatz.ex

defmodule Collatz do
  def of(1), do: 1

  def of(n) do
    IO.puts n

    do_of(n, rem(n, 2))
  end

  defp do_of(n, 0) do
    of(div(n, 2))
  end

  defp do_of(n, 1) do
    of((3 * n) + 1)
  end
end