@Andrews A minor remark on TeX/MathJax.

For divisibility, is think it is better to use $3\mid 6$ than $3|6$. Although not everybody agrees with this, there are some people who prefer the latter. (There is a difference in spacing.)

But $3\nmid 5$ is definitely better that $3\not|5$.

Some discussion about \mid vs. | is in the comments to my answer here: When should each type of vertical bar (pipe) be used?

But I mainly wanted to point out \nmid. (I have already edited one of your posts, I am not sure whether I caught all occurrences of \not|.)

BTW I see that in the meantime quid responded in his room too and that you have also asked in CRUDE (and elsewhere).

@MartinSleziak Thank you, I'm not familiar with commands like \n+... before, I'll notice them in the future.

@MartinSleziak I noticed them as well, thanks for notification.