How do you do expensive off-chain computations?

I’m currently playing around with an idea. I have a set of tokens in mind, which relies on a somewhat complex computation about once a day. Some of the tokens share that same computation result, although not all. How do you calculate this off-chain while still ensuring the whole system is decentralised? The computation can be public, it doesn’t need to be a black box.

Would be great to have some general hints, I know about nothing on the topic.