title: Find all combinations of 1 and 2 that add up to N
body: <p>Say I have a function like this.  I need to know all the combinations of 1 and 2 that will add up to N.  Is there a better way to write this that would perform better for a large integer such as N = 1200 or 12000?</p>
  
  <pre><code>public static int Combos(int n)
  {
      if (n &lt; 3)
      {
          return n;
      }
      else
      {
          return Combos(n - 1) + Combos(n - 2);
      }
  }
  </code></pre>