title: Solving the recurrence T(n) = 2T(sqrt(n))+log2n
body: <p>I would like to solve the following recurrence relation:</p>
  
  <p>T(n) = 2T(sqrt(n))+log2n</p>
  
  <p>Unfortunately, neither the master theorem nor the akra-bazzi-method can be applied in this case. I guess that the solution must be O(log log n) but I am not sure how to prove this.</p>
  
  <p>Many thanks in advance. </p>