[seqfan] Re: Giving a mathematical definition to A280001

[Neil Sloane]

 Since A280001 is being discussed on this list, it is best if we have
a concrete version to look at, so I am going to approve the current
version. Natan, if there are errors that you know about in this
version, please correct them.
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 Fri, Feb 3, 2017 at 9:24 AM, Natan Consigli
<origami.experience at gmail.com> wrote:
> The drawings are three dimensional. In the PDF attached to A280001 there
> are molecules with a dashed and wedge bonds which in chemistry generally
> mean that they point inwards and outwards respectively.
> I'll also attach the link as required by the moderator:
> https://oeis.org/draft/A280001/a280001.pdf
>
> On Thu, Feb 2, 2017 at 11:26 AM, Natan Consigli <
> origami.experience at gmail.com> wrote:
>
>> The drawings are three dimensional. In the attached PDF there are
>> molecules with a dashed and wedge bonds which in chemistry generally mean
>> that they point inwards and outwards respectively.
>>
>>
>> On Thu, Feb 2, 2017 at 7:24 AM, Charles Greathouse <
>> charles.greathouse at case.edu> wrote:
>>
>>> This is a worthwhile project! But I'm not sure that I understand your
>>> question. Being a planar graph is already a standard graph-theoretic
>>> primitive, or is this used in some special way in chemistry?
>>>
>>>
>>>
>>> Charles Greathouse
>>> Case Western Reserve University
>>>
>>> On Wed, Feb 1, 2017 at 12:04 AM, Natan Consigli <
>>> origami.experience at gmail.com> wrote:
>>>
>>> > Also, I have to mention that the graphs are three-dimensional for
>>> > stereoisomer distinction
>>> >
>>> > On Wed, Feb 1, 2017 at 5:57 AM, Natan Consigli <
>>> > origami.experience at gmail.com
>>> > > wrote:
>>> >
>>> > > Dear Seqfans,
>>> > >
>>> > > I am trying to define A280001 mathematically with graph theory. To let
>>> > the sequence be less "obscure" I have to define what does chemical
>>> > aromaticity mean.
>>> > >
>>> > > Here is what I did so far.
>>> > >
>>> > > As far as being a hydrocarbon I am looking for a connected multigraph
>>> > (non looped for some authors) where each node has degree less than five
>>> > (octet rule).
>>> > >
>>> > > For the condition of being aromatic I need a connected subset of nodes
>>> > that satisfies Huckel's rule. This means that such subset must have the
>>> > following:
>>> > >
>>> > > 1) an alternating connection 1-edge/2-edge vertices (conjugated pi
>>> > system);
>>> > >
>>> > > 2) the number of 2-edge connections must be odd (4n+2 pi electrons);
>>> > >
>>> > > 3) the subset of nodes must represent a chemically planar portion of
>>> the
>>> > molecule.
>>> > >
>>> > > I find stating rule 3 in a mathematical way very hard to do. If
>>> anybody
>>> > has ideas I would appreciate your help.
>>> > >
>>> > > Natan Consigli
>>> > >
>>> > >
>>> >
>>> > --
>>> > Seqfan Mailing list - http://list.seqfan.eu/
>>> >
>>>
>>> --
>>> Seqfan Mailing list - http://list.seqfan.eu/
>>>
>>
>>
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/