# How to search for a formula/expression

Suppose I want to search for instances where an expression similar to $x_n^2-x_{n-1}x_{n+1}$ shows up. How would I do that?

I suppose the question goes beyond searching MSE. Are there search engines which handle math formulas in a particularly effective way?

Edit: I am listing some leads in the comments which I found useful:

Uniquation, a mathematical formula search engine. And here is the response to my query above. Perhaps this can be an option on MSE.

• – Martin Sleziak Jul 4 '13 at 14:42
• symbolab.com is another one. – Peter Krautzberger Jul 5 '13 at 17:29
• @PeterKrautzberger Thanks, but when I tried above query on it I could not see a connection between reply and query. Also it is not LaTeX based. Perhaps I am mistaken. Symbolab – Maesumi Jul 6 '13 at 0:16
• Doesn't the math.se search engine match against the raw latex in the posts? – Jack M Jul 9 '13 at 16:12
• @JackM if you are searching for $a^2+b^2=c^2$ the Uniquation seems to also get you $x^2+y^2=z^2$ and the equivalents. So searching a formula becomes a tricky search for a concept. – Maesumi Jul 9 '13 at 21:18
• Another related question at MO: mathoverflow.net/questions/162487/… – Martin Sleziak Apr 6 '14 at 6:45

See my side-project, it is an open-source math-aware similarity search engine.

http://approach0.xyz

I am hoping someone interested can join and form a community to push this project forward, this is the reason I am posting here.

searchOnMath looks interesting too. I think you can do what you want there.

• Is there a search that when you look for $x^y=y^x$ it provides articles with equivalent equations that can be obtained by simple substitutions, such as $a^b=b^a$. That is a search engine that understands the concept of equation beyond just appearance of letters. SearchOnMath is a valuable tool but I do not think it searches for equivalent equations. – Maesumi May 30 '15 at 21:07
• According to a recent announcement on Mathematics Meta, SearchOnMath now indexes MathOverflow and Mathematics Stack Exchange. – Martin Sleziak Feb 1 at 5:10

A few years ago we developed the search engine SearchOnMath, in order to search for mathematical formulas. Recently our tool has indexed both: Mathematics and MathOverflow.

Currently, SearchOnMath is the mathematical search engine with the largest number of indexed sites (including Wikipedia, Wolfram MathWorld, among others ...).

The following video illustrates how it works: SearchOnMath - a brief guide.

P.S.: please, enclose formulas between \${}\$. e.g. \${x+y}\$.

EDIT:

We’d love to hear your feedback. We also posted on Meta.

• This is repeating the entry just above which already has some upvotes. You should delete this one and just add the info there. – Lee David Chung Lin Feb 2 at 2:15