Sequences of Graphs...

[Michael Somos]

seqfans,

The discussion about starting graph sequences at 0 has brought
up some general points. It was pointed out that there is some
problems with starting with n=0 or 1. This is not news to me.
The database was started, contributed to and maintained by
people who are prone to errors. There are still sequences in
OEIS in which there is a mismatch in numbering between the
description, formula, or offset. There are matters of opinion
if Euler transforms should include the a(0)=1 term. The status
of the 'null graph' a real problem, but null sets and before
that number zero itself has been controversial. My opinion is
this. Allow graph sequences to include an a(0) term. If you
don't believe in the null graph then you can ignore it, however
the sequence formula may make sense of the a(0) term. As for
the tree status of the null graph, I think it is a forest and
probably not a tree. Shalom, Michael