Everyone assumes aliens will know higher math. So much so that some people think encoding the orders of the first 26 sporadic groups would be obvious. (IDK why this is better than a list of primes)

But would it, though?
We name the groups by their orders, and think it's neat that exactly 26 are special in this way, like the 5 platonic solids.

But couldn't you do a lot with math and never really focus on these facts? It's not free from culture. math has a culture.