I have no clue what you are asking. What is \(\displaystyle Q_S(n)\)? What is \(\displaystyle N_i\)? What is \(\displaystyle N\)? For the latter two, do you mean \(\displaystyle \mathbb{N}_i\) and \(\displaystyle \mathbb{N}\)? Even still, I have no clue what \(\displaystyle Q_S(n)\) is.