title: Multiply adjacent elements of list and add them
body: <p>I want to successively multiply adjacent element of the list and add the multiplication:</p>
  
  <ul>
  <li><code>([1,2,3,4])</code> should perform <code>(1*2+2*3+3*4)</code>, and </li>
  <li><code>[1,2,3]</code> I want to get <code>8</code> because <code>(1*2)+(2*3)</code></li>
  </ul>