title: Using recursion to add odd numbers
body: <p>I am trying to write a method to calculate the sum of the odd numbers in all the numbers less than the given number. so eg. CalcOdd(7) would return 5 + 3 + 1 = 9. CalcOdd (10) would return 9 + 7 + 5 + 3 + 1 = 25 etc</p>
  
  <p>The method needs to take in a number, subtract 1, then recursively work backwards adding all odd numbers until it reaches 0. This is what I have so far.</p>
  
  <pre><code>    private static int CalcOdd(int n)
      {            
  
          if (n &lt;= 1)
              return 1;
          else
              if (n % 2 == 0)
                  n--;
  
          return n + CalcOdd(n - 2);
      }
  </code></pre>
  
  <p>It doesn't work so well, it includes the number passed in in the addition which is not what I want. Can anyone suggest a better way of doing this ? I would also loke to be able to port the answer to work for even numbers and add the option to include the original passed in number in the answer.</p>
  
  <p>Many thanks</p>