[seqfan] Re: A064513, A058201, and the graph degree/diameter problem.

[Neil Sloane]

Allan, Chris,
Thanks for those comments.
I "deaded" A058201, and I'm revising A064513.

My old notes there say that it is known that a(7)=50. Do you believe that?

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 Tue, Nov 17, 2015 at 11:03 AM, Allan Wechsler <acwacw at gmail.com> wrote:

> I apologize for getting the values backwards. It is as Chris Thompson says:
> the old sequence says 25 and is wrong, and the new one says 24, and is
> right, agreeing with all online sources I have consulted.
>
> But a(2) still ought to be 5, not 4.
>
> On Tue, Nov 17, 2015 at 9:37 AM, Chris Thompson <cet1 at cam.ac.uk> wrote:
>
> > On Nov 17 2015, Allan Wechsler wrote:
> >
> > [... snipped...]
> >
> >> Wikipedia has articles on the degree/diameter problem. The first column
> of
> >> their table (
> >>
> >
> >
> https://en.wikipedia.org/wiki/Table_of_the_largest_known_graphs_of_a_given_diameter_and_maximal_degree
> >
> >> ) gives values 2, 5, 10, 15, 25, 32, 50. So their a(5) agrees with the
> >> later
> >> sequence on OEIS, but their a(2) (and *my* a(2), for that matter!)
> >> disagrees with *both* versions on OEIS.
> >>
> >
> > I read the Wikipedia page as saying that a(5) = 24 - admittedly the dark
> > blue background could easily lead to misreading!
> >
> > In any case, that agrees with the EJC Dynamic Survey (updated 2013). The
> > Wikipedia link to that seems to be broken: a working one is
> >
> > http://www.combinatorics.org/ojs/index.php/eljc/article/view/DS14
> >
> > This also confirms a(6) = 32 as optimal.
> >
> > --
> > Chris Thompson
> > Email: cet1 at cam.ac.uk
> >
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> >
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> >
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