Italicization of single letter variables and specifically Big O notation

[suragch]

I assume it is correct to italicize single letter variables that are not specifically used in code:

• There are n items in the array. (correct)
• There are n items in the array. (incorrect)

Does this apply to the O used in Big O notation? Here are some common examples:

• O(1)
• O(n)
• O(n²)
• O(log n)
• O(n log n)

Are the following correct:

• O(1)
• O(n)
• O(_n_²)
• O(log n)
• O(n log n)

_O_(1)
_O_(_n_)
_O_(_n_²)
_O_(log _n_)
_O_(_n_ log _n_)

[suragch]

https://guides.raywenderlich.com/article-author-guide/prepare-to-write/follow-our-formatting-conventions

[suragch]

The official guides don't seem to support it.

But also note that the current version of Data Structures and Algorithms in Swift does use italics. And see the usage here: https://en.wikipedia.org/wiki/Big_O_notation