The last time I wasted some time on this I had a similar notion: "start big" with numbers on the order of 1 million bits and try and demonstrate that different

The last time I wasted some time on this I had a similar notion: "start big" with numbers on the order of 1 million bits and try and demonstrate that different sections of those bits (prefix,middle,suffix) change according to some pattern that can then be generalised "down" to just 64 bits, which has been manually tested.