I might be wrong but there is no something like O(2n) only O(n), which means it is proportonal to no matter if the concret steps are n/x or nx where x is a constant.
sorry! its actually 2 to the power of n ( nsqaure) I forgot and didn't check it properly. I wont make this mistake again.
Maybe use n (pow) 2? Or can you please suggest the better representation?
BTW Thank you for reading. Its my first blog.