title: How to get O(nlogn) from T(n) = 2T(n/2) + O(n)
body: <p>I want to calculate <code>O(n log(n))</code> without using the master theorem.</p>
  <p>Does anyone know a mathematical way of calculating <code>O(n log(n))</code> from the  recursive formula <code>T(n) = 2T(n/2) + O(n)</code>?</p>