4:30 PM
@MartinSleziak Thank you! I am even considering to focus on my search engine full time, e.g. to do a math QA website in China. However, I do not have much confidence to quit my job for now.
@MartinSleziak I assume this is not a bug. First, by "adding something more to the query" you mean adding another keyword, by default, Approach0 uses OR instead of AND to search keywords. If you get that post by using the second query, then the first keyword ($n>\dfrac{p_n}{\ln p_n}$) perhaps does not contribute to your search results at all. (This is also indicated by the search results without any math expression being highlighted)
Second, when I get to that post by this single query: approach0.xyz/search/…

Ok, I did not now about or.
But still, why the query using formula copied directly from the post does not find it?
I mean this formula, which is part of the body of that question: $n>\dfrac{p_n}{\ln p_n}$. If I search in Approach0, I get no results.

Not finished my second point yet, when I get to that post by this single query, I see that post in top of my result, but notice that post does not have that piece of formula you are talking about in its title at the time it is indexed

Here is how source of the question looked in 2014.

which means the post author may have edited and changed the title.

It contained that formula.
It is true that it was edited into the titleonly recently, but you can see that it was already in revision from October 2014 in the body of the question.

4:46 PM
OK, I get your point, what I am talking about is the title from search result title shows that Approach0 indexer misses (for whatever reason, maybe the author changed the tile to simply "Remarks on a Previous Post" in the meantime) to index the complete title.
But I notice that formula is indeed in the content of that post, so this is possibly a bug. But I need to spend some time to investigate this issue. Again, this is midnight in Beijing time, I may take some time to look at this problem later. But thanks for reporting this problem to me, as always.

Thanks for looking at it. Of course, it is not an urgent thing.
But I thought that when I see that something behaves differently from what I would expect, it might be worth mentioning here.

Sure, your suggestions actually help Approach0 improve a lot! I still appreciate all these suggestions/reports you have posted.
Going offline. Have a good day!

See you!