My question is, how would one go about finding such a number?
This is obviously very open-ended, but here are some possible specifications.
- It was important that the number was prime, because we mathematicians live for that sort of thing.
- It was important that the number of digits was relevant. In this case, it was 1350 (as mentioned in the video).
- It should be very suitable for ASCII art, that is, it should be filled with 0's and some other digit for the most part (in some base, preferably 10).
We obviously allow some "impurities", such as the 1 at the end of the number and the 621 in between, but in general we want our number to roughly meet the requirements.
As far as I understand, this is computationally extremely difficult, and I can't think of any theorems that would help in this venture. Just finding all primes of length 1350 is computationally intensive, and the other restrictions seem to make it even harder.
Even if this number was just found, I imagine that computers find numerous long primes all the time, and the fact that this number was found to have this property requires some amount of "human pulling a rabbit out of a hat". How would one find look at a list of primes and find such properties?
I apologize if this question is too soft, but I do not know of any computational methods that seem even remotely helpful, and I would like to learn more.
I have already looked at Brady's video description that says
Professor McKee explains: "Most of the digits of p were fixed so that: (i) the top two thirds made the desired pattern; (ii) the bottom third ensured that p-1 had a nice large (composite) factor F with the factorisation of F known. Numbers of this shape can easily be checked for primality. A small number of digits (you can see which!) were looped over until p was found that was prime."
but can anyone tell me what is exactly going on behind the scenes in there?