title: total number of ordered tree with 3 nodes
body: <p>I am getting mixed answers on internet</p>
  
  <ol>
  <li><a href="https://in.answers.yahoo.com/question/index?qid=20100508110438AAbKyMj" rel="nofollow noreferrer">https://in.answers.yahoo.com/question/index?qid=20100508110438AAbKyMj</a></li>
  <li><a href="http://wiki.answers.com/Q/How_many_ordered_trees_are_possible_with_3_nodes?#slide=2" rel="nofollow noreferrer">http://wiki.answers.com/Q/How_many_ordered_trees_are_possible_with_3_nodes?#slide=2</a></li>
  </ol>
  
  <p>I also saw a question at <a href="https://stackoverflow.com/questions/18153740/what-are-the-total-number-of-possible-ordered-trees-with-n-nodes">SO</a> but it didn't helped me much</p>
  
  <p>What should be the answer?</p>
  
  <ul>
  <li><p>Also is this a tree?</p>
  
  <pre><code>    a
     /
    b
   /
  c
  </code></pre></li>
  </ul>