title: Find free number in a range
body: <p>I have a range of numbers (say, 20-100). Lets say the following are occupied: 20, 21, 22, 24. 25, 26, 28. </p>
  
  <p>I ask the user how many free numbers he wants. Lets say, he says three numbers. So my output should be 23, 27, 29.</p>
  
  <p>How can I quickly do this with powershell?</p>
  
  <p>Thanks!</p>