Re: The next exercise

[Michael Heerdegen <michael_heerdegen@web.de>]

Emanuel Berg <incal@dataswamp.org> writes:

> > 2^2^43 - 1, right? What's it? It's too large to be the
> > largest known prime number, or I calculated wrong. I don't
> > know. Tell us.

At least I know now it's not a prime, since all integers of the form
2^2^n - 1 are divisible by 5.

> Hint 1: Start with (** 2 10) which is 1024.
> Hint 2: Think computers, not math ...

Is it some kind of Turing test?  No, I'm not a computer, I swear.

Hmm, what might I think about it as a computer?  2^2^43-1 is binary

  1 1 .....................1
  \_______________________/
   8 796 093 022 208 digits 1

so as a computer I would no doubt think, oh man, look at these
8 796 093 022 208 digits "1", I wounder what this is about - is it a
prime?  But I already answered that.  Hmm.

Still too mathematical maybe.  Wait - it's the largest number a
calculator using 8 796 093 022 208 binary digits can express.

The horizontal checksum of this binary number is 2^43 - this is not some
kind of "the answer is 42" joke?

I'm not a good computer.  I would obviously fail the inverse Turing test
(as a human pretending to be a computer).


Michael.