It's a post-biological pidgin. You can't communicate cultural ideas to beings that probably have entirely different ideas of culture, but you can establish the intent to communicate as two rational species. Since mathematics is presumably consistent across the universe, you can beam a non-natural signal into space as a technosignature. If something responds to it, you're both sentient and have some kind of respect for academia. You can then use it to establish logic, make grids, and represent simple images without relying on their "eyes" perceiving the same wavelengths we do. Something like 1s and 0s is probably going to be easier for them to interface through than speech.