title: I have a problem writing the code for a C++ program for natural numbers
body: <p>I have some difficulties making the code for my homework assignment.
  The program should contain at least 2 functions and should do this:</p>
  
  <ul>
  <li>reads a natural number n </li>
  <li>and prints out the sum: 1 + 2.3 + 3.4.5 + 4.5.6.7 +...+ n.(n + 1)...(2n - 1). 
  Thanks!</li>
  </ul>