title: Big O notation for exponential and logarithmic complexity
body: <p>There are a lot of questions about big O notation, but I didn't found clear answer for this question.</p>
  
  <p>We write that:<br/>
  O(5n) = O(n)<br/>
  and<br/>
  O(3n^2 + n + 2) = O(n^2)</p>
  
  <p>Can we write that:<br/>
  O(2^(2n)) = O(2^n)?</p>
  
  <p>The same for logarithmic complexity:
  O(n log(4n)) = O(n log(n))?</p>