# [seqfan] Mystery concerning sequences A169720-A169727

Robert Munafo mrob27 at gmail.com
Sun Dec 2 06:45:28 CET 2012

```While Doug was writing his reply I "cracked" two more of these and
created an illustrative web page:

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

The basic problem with these sequences is that the diagrams provide
too little, and at the same time too much, information. The diagrams
are confusing to the point of being misleading.

On 12/2/12, Neil Sloane <njasloane at gmail.com> wrote:
> Doug, Thanks very much - that clears
> up the mystery! Nice work! (I had not thought to use
> the pieces in multiple ways)
> Neil
>
> On Sat, Dec 1, 2012 at 11:25 PM, D. S. McNeil <dsm054 at gmail.com> wrote:
>> > But how are the sequences obtained from the drawings?
>>
>> A169720 seems to count the number of contained shapes from the inside
>> out:
>>
>> 1 = 1 central hexagon
>> 10 = 1 hexagon + 6 small triangles + 3 triangles containing the central
>> hexagon
>> 55 = 10 + 12 white triangles/hexagons + (3 tri + 1 hex) * 6 inside the
>> green/blue triangles + 6 green/blue triangles + 3 large triangles
>> containing the white hexagon = 22+24+9=55
>>
>> etc.
>>
>> Doug

--
Robert Munafo  --  mrob.com