title: puzzle: N persons sitting on round table. No of ways of handshakes without crossing any other handshakes
body: <p>We have n persons sitting on a round table. Any person can do a handshake with any other person. In how many ways these n people can make handshakes so that no two handshakes crosses each other.</p>
  
  <p>I found this puzzle in a technical interview forum, but no answer. One way i could think of was find all the permutations of handshakes and then check each permutation whether it satisfies or not.</p>
  
  <p>Can anyone please sugget any other solution which is more efficient.</p>
  
  <p>@edit: Clarification from comments: N would be even.</p>