But you can have easy examples like does the decimal reprensentation of pi contain four zeros in a row. I think we dont know if it is true, so you wouldnt know

But you can have easy examples like does the decimal reprensentation of pi contain four zeros in a row. I think we dont know if it is true, so you wouldnt know if your algo stops if you dont run it (and it stops). No need for self referential programs.