Researchers often prove theorems but they don't know whether somebody else already published the same result.
One strategy is to read papers on the topic or search keywords, however it would take way too long to read all the papers on one's subject and some of them might not even be accessible (e.g., one might need to buy a journal in a foreign country).
So it would be great if there is one resource which indexes papers with their results. The results would have to be written in an universal language. Many results in Math and CS can be reduced to set theory, so the results could be stated as a formal sentence of set theory. If such resource exists, a researcher would simply need to state their result formally in a specified language and he would quickly find whether someone else already published their result.
Does something like this exist? If not, I think that's surprising.