[seqfan] Re: Changes to b-files and the rules [b-file lengths]
njasloane at gmail.com
Sat Nov 24 05:56:19 CET 2018
I did not agree with Neil Greubel's suggestions about putting restrictions
I did not agree with them, and I do not think we should even mention them
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 Fri, Nov 23, 2018 at 8:16 PM Chris Thompson <cet1 at cam.ac.uk> wrote:
> Extract from Neil Gruber's message of 14 November:
> >3) B-files should have appealing, and generally "nice", lengths. The
> >most often seen lengths are 1000 terms, 2500 in some case when higher
> >amount of terms is time consuming, 5000 and 10000 terms. Term lengths
> >for triangles, for a typical triangle of anti-diagonal, follow the
> >pattern binomial(n+1,2) for n rows. Not-so-nice term lengths may occur
> >when the digit length nears 1000 decimal places sooner than a typical
> >length of 1000 terms.
> (and later)
> >3) A bulletin should be added which reads (or near to) " B-files of
> >length larger than 10000 terms needs to be approved by and EIC unless
> >otherwise directed by an EIC or bureaucrat.
> This caused me to look at b-files that I have submitted in the past with
> un-"nice" lengths. I found essentially two cases:
> A030979 is the n such that C(2n,n) is coprime to 3*5*7. These have a
> distinctly fractal distribution, with large gaps. I think I was planning
> on a b-file of at least 1000 entries, but big gaps occur after 699 values
> and then after 1374. It seemed quite unnatural to chop the b-file off
> in the middle of a cluster.
> There is a set of 10 sequences related to the "sum of n consecutive squares
> equalling a square" problem, which one could arrange as
> A001032 A001033 A134419 (n values)
> A007475 A056131 - (corresponding x values)
> A076215 A056132 - (corresponding y values)
> A274469 A274470 A274471 ("missing" n values)
> The b-files I submitted were for all n values up to 250000 (earlier 30000)
> which makes the lengths not particularly "nice" (and some of them are
> a little over 10000). The values for the different columns are computed
> by a single program (using the Pellian equation described in A134419).
> I suppose it would have been possible to truncate the results to
> individually "nice" lengths, but it didn't seem natural to me at the
> time. In any case, the sequences in the last row ("missing" n values)
> would not have "nice" lengths unless the upper limit chosen were different
> from those in the first row, which seems even less natural.
> Chris Thompson
> Email: cet1 at cam.ac.uk
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