title: Batch File/Script Delete every 3 files in a directory
body: <p>I have a folder with sequentially named images (a0001, a0002, a0003, etc.) and I was wondering if there was a way to delete every 3 files without touching the others.</p>
  
  <p>So for example, I have: a0001, a0002, a0003, a0004, a0005 a0006, a0007, a0008, a0009</p>
  
  <p>And after I would like to have: a0001, a0005, a0009</p>