Even if you don't want to draw the Entire recursive Tree, Just visualize it as the Root Node is Working on O(n2) complexity where as the child will work on 9/16*n2 Complexity that will be decreasing until you reach the farthest child or we can say the Leaf.
And that certainly will be less than O(n2) and we can neglect it.
So the Answer should Be : O(n2)