You can simply say grows as n⁷. Although people will understand what you mean by saying O(n⁷), O is an upper bound, not a lower bound. What you should say if y

You can simply say grows as n⁷. Although people will understand what you mean by saying O(n⁷), O is an upper bound, not a lower bound. What you should say if you want to be correct is it grows as Ω(n⁷).