title: All combinations of ranges given an 'anchor' and 'reach'
body: <p>Let's say I have an 'anchor' number of 8, and a 'reach' number of 2. What's the best way to produce a python list of lists as below? The 'reach' number is the maximum number of digits away from your 'anchor' number you wish to generate combinations for. </p>
  
  <p><code>[[8], [8,9], [8,9,10], [7,8], [6,7,8], [7,8,9], [6,7,8,9], [7,8,9,10], [6,7,8,9,10]]</code></p>
  
  <p>Note that I don't want <code>[6, 8]</code> or <code>[8, 10]</code> or <code>[6,8,9]</code> etc. because there are numbers missing in between.</p>
  
  <p>Order doesn't matter for the lists or the lists-of-lists.</p>
  
  <p>Thanks!</p>