title: How to first remove every second element on a list, then every third on whats remaining?
body: <p>Say:</p>
  
  <pre><code>list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  </code></pre>
  
  <p>I know that <code>list[::2]</code> would remove every second element, so <code>list = [1,3,5,7,9]</code>
  What if say I then needed to remove every third element? So list would become <code>[1,3,7,9]</code> (5 would be removed since it is the third element. How would I then proceed to do that?
  Currently, using <code>b = list[::3]</code> returns <code>[1, 7]</code></p>