title: Undocumented Excel Formula Syntax? =Rx:Ry
body: <p>I noticed this weird formula syntax in on of my inter-company Excel template.  One of the cells contains a formula like </p>
  
  <pre><code>=5:10
  </code></pre>
  
  <p>Excel seems to recognize this as a formula but it errors out.  What is going on here? Seems like maybe it's trying to sum up everything in rows 5 through 10 maybe?</p>