I've been trying to figure out this but I don't know how to tackle the inductive process,
So I have numbers defined recursively as it follows:
For $C_1=0$ and for $n>1$
$$C_n=4C_{\lfloor n/2 \rfloor}+n$$
Where $\lfloor n/2 \rfloor$ is the floor function.
After that definition, I have to prove that
$$C_n \le4(n-1)^2 \ \forall n \in \mathbb N$$
I already proved for the base $C_1$, but I don't know how to approach it from there. Thanks any help! (: