[seqfan] Re: Counting simple graphs with node degree >=2

Frank Adams-Watters franktaw at netscape.net
Wed Sep 16 17:58:25 CEST 2015


As usual with unlabeled objects, the connected and total (not necessarily connected) sequences are related via the Euler transform.

Franklin T. Adams-Watters

-----Original Message-----
From: Richard J. Mathar <mathar at mpia-hd.mpg.de>
To: seqfan <seqfan at seqfan.eu>
Sent: Wed, Sep 16, 2015 8:34 am
Subject: [seqfan] Re: Counting simple graphs with node degree >=2


See http://list.seqfan.eu/pipermail/seqfan/2015-September/015292.html:

Prompted
by Neil, Brendan McKay has come to the same conclusion
(priv. commun.) and
contributed another variant in A261919 which allows graphs
to have more than one
component (to be disconnected).
The first difference between A261919 and A004108
is at a(6), because on 6 nodes
we may have two disconnected triangles which
individually fulfill the
requirements.

Richard
Mathar

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