Here's what I found so far
approach0.xyz : offline
searchonmath.com : Gives irrelevant results such as p = m v when searching for F = m a
https://search.mathweb.org/: A collection of abandoned projects and offline sites
+1 to wolfram alpha. But just like Chegg, I thought wolfram alpha would be harshly affected by the AI disruption.
I used it a lot in college but never since. Are current college folks still using it?
sure are
The encyclopedia of integer sequences can be quite useful: https://oeis.org/
Slightly related: https://oeis.org
ChatGPT and family has been effective for me, even to connect equations I’m familiar with to areas I hadn’t encountered before.
If the formula generates an integer sequence, then searching that sequence on OEIS should give a lot of good information.
Wolfram Alpha
Claude