e
        firing rate of a single neuron, which has a feedback connection to
        itself.  $\tanh$ is the activation (sigmoidal) function of the neuron,
        and $w$ is the weight of the synaptic feedback.</p>

        <p>Experiment with it for yourself:</p>
        <script>document.write(notebook_link('pend', "autapse"))</script>
  
        <p>As I've also provided the equations of an <a
        href="https://en.wikipedia.org/wiki/Long_short-term_memory">LSTM</a>
        unit that you can also experi