[seqfan] Re: Java implementations update

[M. F. Hasler]

SeqFans,

this jOEIS approach is certainly interesting, but I would like to propose a
different approach aloready mentioned years ago here and on the wiki.
As proof of concept, I make available an example OEIS_js web page at
https://github.com/m-f-h/OEIS.js which you can download on your computer.
This page looks exactly like any random page of OEIS.org search results,
with two major differences:
- it has two buttons: [EXTEND] in the DATA section and [PARI] in the
PROGRAM section
- the HTML source is 250 lines instead of 550 lines (and the main content
is in less then 100 lines as opposed to about 400 lines in the original).

The main feature are the [EXTEND] and [PARI] buttons, which can be clicked
to add terms to the DATA section, resp. to add PARI/GP code in the PROG
section.

This is done by just calling one single javascript function oejs(). This
function is *completely independent* of the sequence and will work with NO
CHANGE for any other sequence (for the moment "only" for the 30 000+ linear
recurrent sequences -- but it is just a quick hack written in 1-2 hours).
It fetches the signature of the recurrence from the LINKS section and uses
this to extend the DATA or to produce the PARI code (using the minimal
number of initial values from DATA).

Obviously, extending the DATA term by term is just meant to show that it
works.
The main use would be to produce a b-file (or some more practical format,
on request) of arbitrary (user-defined) size.

I insist on the main characteristic (as opposed to the jOEIS approach)
which is to have one single, *sequence-independent* function.
Also, this improvement would greatly reduce server load and traffic. (The
script works on the user's computer, and could be put as separate file on
the server (as could/should  the CSS) so it would be cached by the users'
brower and make the HTML page even 100 more lines smaller.)

See the REAME file on github for more information and possible extensions.
I'd be glad if this could find interest by others to be developed.
In particular, I remember that Charles knows how to add a script as
extension to your browser, which would make it possible to use this extra
functionality even without waiting for it to get officially added to the
main OEIS -- but I hope this could be done sooner or later.

Among many others, one major advantage would be to get rid of the many
submissions of trivial PARI, MAGMA, Mmca, ... scripts, g.f.'s and
recurrence formulas: these (the trivial ones!) could and should be produced
on-the-fly, allowing to make improvements in one single place that would
immediately have site-wide effect.
The script could/should also make consistency checks w.r.t. existing
FORMULAs etc. and in that way contribute to consolidation of the OEIS.

A word to those who'd object that it's only useful for linear recurrences:
that's the case for this proof-of-concept quick hack, but obviously it can
be extended to many other classes, and actually there's an easy way to
extend the functionality to theoretically /any/ sequence, namely, by adding
JS (or other suitable) code in the PROG section, which the script could
recognize and use.

Last not least, I should also say that the goal is not to get rid of user
contributions, but on the contrary, to be able to focus on *nontrivial*,
interesting contributions, and to dedicate the required care and time to
these.

(This approach could also benefit from work already done in the  jOEIS
framework: code written for these implementations could help to extend
functionality to "nontrivial" cases.)

- Maximilian

On Tue, Jun 18, 2019 at 6:00 PM Sean A. Irvine wrote:

> Thanks to recent contributions by Georg Fischer, the collection of Java
> programs for OEIS sequences (jOEIS) now has implementations for over 58200
> sequences, especially concentrated in A-numbers less than A024000.  We are
> currently covering about 1/6 of all sequences.
>
> The main aim of the project is to validate sequence data in the OEIS.
> The entire project is available on github:
> https://github.com/archmageirvine/joeis
>
> To the extent possible, these implementations are regularly tested against
> the data lines in the corresponding sequences.  Georg has done extensive
> testing against b-files, leading to numerous corrections in the OEIS (and
> to be fair, in the implementations as well).
>
> Georg and I are looking for additional contributors of Java code or of
> other algorithms which cover some number of sequences.  The following link
> is those A-numbers below A024000 for which we do not currently have an
> implementation:
>
> https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/notdone.dat
>
> Some of these are inherently hard, but in many cases it is lack of
> information that prevents implementation.  Many currently have no useful
> program (or formula) in any language and are thus good candidates for
> general improvement in the OEIS.
>