[seqfan] Re: Polyominoes (A000105, A000988, A001168) - offset problem

Jack Grahl jack.grahl at gmail.com
Thu Jun 25 12:49:41 CEST 2020

Notwithstanding what Wikipedia should do here, I think that the OEIS should
always include a zero term when this has basic mathematical validity (ie
for most combinatorial objects - providing that an instance with zero
elements can be described without contradiction). This makes the
encyclopedia much more useful, since relating a sequence to other
definitions, generating functions, and so on is a basic use of the
encyclopedia. The 'offset' info makes it easy to neglect these terms if you
want to.

On Thu, 25 Jun 2020, 10:16 Brendan McKay, <Brendan.McKay at anu.edu.au> wrote:

> Hi Neil,
> Anyone who sees an error on Wikipedia, and knows how to fix it but
> doesn't, is
> responsible for the error.
> But in this case there is no error.  Wikipedia follows "reliable
> sources" and in this case
> the reliable source is Golumb's book "Polyominoes".  From a brief look
> it seems that
> Golumb does not recognise a null polyomino (see Fig 1 and Tables 3 and
> D.1), so
> Wikipedia is *required* to either also disallow it or to change to a
> different source.
> Incidentally, the first comment on A0000105, which is
> "A0000105(n) + A030228(n) = A000988(n)", is not correct for n=0 at the
> moment.
> Cheers, Brendan.
> On 25/6/20 5:27 pm, Neil Sloane wrote:
> > Everything in the Wikipedia is inaccurate.
> --
> Seqfan Mailing list - http://list.seqfan.eu/

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