[seqfan] Mystery concerning sequences A169720-A169727

Robert Munafo mrob27 at gmail.com
Mon Dec 3 05:12:49 CET 2012


Okay, well here's an alternative interpretation which I think is a
little better:

Look at the central hexagon, and see how it's part of a "star of
David". The Star of David is two triangles, and the hexagon itself is
the third object. So you could count that as 3 items.

On 12/2/12, D. S. McNeil <dsm054 at gmail.com> wrote:
>> I don't get the part where you count "3 triangles containing the
>> central hexagon", and "3 large triangles containing the white
>> hexagon". In each case I only see two triangles in the image at
>> oeis.org/A169720/a169720b.jpg  If you're counting a triangle twice,
>> why not count both of them twice?
>
> I simply worked backward from what it looked like I needed to count in
> order for the total to be right.  There are three points on one side
> of the vertical axis which can serve as the peak of a triangle, I
> needed the number three, so I decided that was how they were to be
> counted.  I could be as easily convinced it's really 2 such triangles
> + 1 of something else.
>
> BTW, those are some gorgeous pictures on your page!

It's just ASCII graphics... but thanks :)

  http://www.mrob.com/pub/math/seq-a169720.html

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