system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: With world record calculations of pi, how can we be sure that the digits calculated are accurate to the extent claimed?

For example, if someone claims to have calculated the new world record for digits of pi (or some other irrational number), how can we be sure that they didn't just make up the numbers? What structures are in place to double check that the digits are accurate without the ability to cross check it with the "true number"?
gpt
Short of, as you hinted, actually calculating it yourself, there are algorithms (google "Bailey-Borwein-Plouffe" if you want the gory details) which allow you to calculate the n-th digit of pi without knowing the preceding digits.  Using this, one can spot-check random digits until they're satisfied it looks good.