[A058387] Series-Parallel Confusion
Gordon Royle
gordon at csse.uwa.edu.au
Fri Nov 8 03:36:43 CET 2002
I am confused about A058387
http://www.research.att.com/cgi-bin/access.cgi/as/njas/sequences/eisA.cgi?Anum=A058387
which lists the numbers of series-parallel networks on n unlabelled edges
with no multiple edges.
According to this there are
0 on 0 edges
1 on 1 edge (x---x)
1 on 2 edges (x---x---x)
2 on 3 edges..
But according to the definition of series-parallel with which I am familiar
we should have 3 here - a path of length 3, a 3-star and a triangle.
Can anyone shed any light here? Is "network" simply a synonym for "graph"
(or "connected graph")?
Is there a sequence of "simple series-parallel graphs" by number of vertices..
(I get 1,1,2,5,15,54,227... and want to make sure my program is correct).
Cheers
gordon
--
Dr. Gordon F Royle, http://www.cs.uwa.edu.au/~gordon, gordon at cs.uwa.edu.au
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