The outer loop executed log(Base2)n times.so it is O(log(Base2)n).
the inner loop executed k times for each iteration of the outer loop.now in each iteration of the outer loop, k gets incremented to k*2.
so total number of inner loop iterations=1+2+4+8+...+2^(log(Base2)n)
=2^0+2^1+2^2+...+2^log(Base2)n (geometric series)
=2^((log(base2)n+1)-1/(2-1)
=2n-1.
=O(n)
so the inner loop is O(n).
So total time complexity=O(n), as O(n+log(base2)n)=O(n).
UPDATE:It is also O(nlogn) because nlogn>>n for large value of n , but it is not asymptotically tight. you can say it is o(nlogn)[Small o] .