First of all sorry if this has been posted before, I found lots of master theorem questions on the search but not one like this. I am familiar with master theorem but a little uncomfortable with substitutions and I can't seem to think of one for this. I tried to unravel the recursion a bit to find a hint and found $$ 3B(\frac{n}{\log_2^nn})+\frac{n}{\log_2^{n-1}n} $$ at depth $n$ (this could be incorrect though, I don't do that often.) Can somebody give me a hint of a substitution please?
Thanks