[seqfan] Re: A program to compute A002845

[Neil Sloane]

Max Alekseyev (I'll copy this to him) had a way of handling - and
comparing, which
is tricky - numbers which are sums of towers.  This comes up in our work on
the Kaprekar problem.

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com



On Wed, Jan 30, 2019 at 8:24 AM Vladimir Reshetnikov <
v.reshetnikov at gmail.com> wrote:

> Today I published a program on GitHub that computes elements of
> https://oeis.org/A002845 (Number of distinct values taken by 2^2^...^2,
> with n 2's and parentheses inserted in all possible ways).
>
> https://github.com/VladimirReshetnikov/Oeis.A002845
>
> It uses a special representation of numbers that allows to efficiently
> manipulate high power towers, but is still brute force in the sense that it
> enumerates and stores all possible outcomes for each n. So far I was able
> to confirm all values currently listed (up to n=27), and I estimate that I
> would need a machine with more than 100GB RAM to compute the next.
>
> I would be delighted if anybody could improve my solution, port it to other
> programming languages, or provide computational resources.
>
> --
> Best regards
> Vladimir Reshetnikov
>
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