Recurrence relation (not solvable by the master theorem)
Wikipedia has a slight extension of the master theorem which covers your case: case&nbsp;2b here.
For the recurrence $T(n)=aT(n/b)+f(n)$ where $f(n)=\Theta(n^{\log_b a}/\log n)$, it gives $T(n)=n^{\log_b a}\log\log n$.