[seqfan] Re: A002094 from 1875 needs more terms

Hugo Pfoertner yae9911 at gmail.com
Sun Mar 18 07:34:34 CET 2018


At the moment, the link
http://www.mpia-hd.mpg.de/~mathar/public/mathar20180317.pdf
doesn't point to the illustrations of the first terms of A002094, but to an
article
NO COMMON TERMS IN THE SEQUENCES sigma (p^i) AND sigma(p^(i+1))
AS p RUNS THROUGH THE PRIMES.

On Sat, Mar 17, 2018 at 10:12 PM, Sean A. Irvine <sairvin at gmail.com> wrote:

> I get by explicit computation
>
> 2, 5, 10, 25, 56, 139, 338, 852, 2145, 5513, 14196, 36962, 96641, 254279,
> 671640, 1781840
>
> Computed by using nauty to generate trees of maximum degree 4, then either
> adding one edge making a multigraph or one edge to make a cycle.  This
> matches the more extensive set of terms computed by R. J. Mathar.
>
> Sean.
>
> On 18 March 2018 at 07:20, Neil Sloane <njasloane at gmail.com> wrote:
>
> > Richard, Thanks for figuring out the correct definition!  I have changed
> > the definition accordingly.
> >
> > It would be nice to have more terms, even if they were found by direct
> > enumeration using one
> > of the methods that Richard suggests - both as a check on Schiff's
> values,
> > and in the hope
> > that given enough terms we could guess a generating function.
> >
> > 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 Sat, Mar 17, 2018 at 1:08 PM, Hugo Pfoertner <yae9911 at gmail.com>
> wrote:
> >
> > > The German in Schiff's article is difficult to understand, but it is my
> > > impression that at the time of writing the meaning of "alcohol radical"
> > was
> > > different from the modern use, where it means an "-OH" attached to a
> > > hydrocarbon.
> > > https://www.britannica.com/science/alcohol/Structure-and-
> > > classification-of-alcohols
> > > So perhaps the name of the sequence should be adapted to modern
> chemical
> > > terminology and "alcohol" be dropped. The title of Richard's
> > illustrations
> > > might be a candidate for a less misleading sequence title.
> > >
> > > Schiff 's Hydrocarbons with a Single Ring
> > >
> > > Hugo Pfoertner
> > >
> > > On Sat, Mar 17, 2018 at 5:44 PM, Richard J. Mathar <
> > mathar at mpia-hd.mpg.de>
> > > wrote:
> > >
> > > > In response to http://list.seqfan.eu/pipermail/seqfan/2018-March/
> > > > 018463.html :
> > > >
> > > > As an appetizer I added illustrations for the first few terms (as far
> > as
> > > I
> > > > understand the compositions) to http://oeis.org/A002094 .
> > > >
> > > > RJM
> > > >
> > > > --
> > > > Seqfan Mailing list - http://list.seqfan.eu/
> > > >
> > >
> > > --
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> > >
> >
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> >
>
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