title: how many graphs with 10 nodes and 2 edges
body: <p>Preparing for exam I have a problem with the following exercise:<br/>
  How many undirected graphs with exactly 10 nodes and 2 edges exist? </p>
  
  <p>My approach:<br/>
  I need 3 or 4 nodes to draw 2 edges.<br><br/>
  So I have <br/>
  <br/>10 choose 3 = 120
  <br/>And 10 choose 4 = 210 
  <br/>= 330 possibilities?!
  <br/><br/>Is that correct or did I miss something?</p>
  
  <p><b>Edit:</b> orphaned nodes are allowed </p>