[seqfan] Re: Toothpick sequences (again)

Benoît Jubin benoit.jubin at gmail.com
Thu Jun 11 01:00:39 CEST 2009


Thanks for the answers.  Now, I understand  A160120, A160160, A160170,
A160406, A160408 (and their respective first-differences).  I think
these comments are worth adding to the OEIS entries, especially for
A160160 and A160170 (or maybe they are already undergoing the
submission process).

Benoit


On Thu, Jun 4, 2009 at 3:25 PM, Omar E. Pol<info at polprimos.com> wrote:
> Benoit,
> In the entry A160120 a Y-Toothpick is as a toothpick but with three
> endpoints (a propeller).
> On june 01 2009 I sent to the OEIS several comments lines and two
> illustrations about this sequence.
> Note that in the Y-Toothpick sieve we can see distinct polygons, with side
> length = 1, for example:
> - Triangles
> - Rhombuses
> - Concave-convex hexagons
> - Concave-convex dodecagons
> - ...
> It appears a sieve with holes!.
>
> ==========
>
> David,
> About the toothpick sequence A139250:
> For the area, see A159786.
> For the number of cells, see A147614.
> For the number of rectangles, see A160124.
>
> ==========
>
> Franklin,
> I agree with you. In the entry A160160 there is a rotation of axes:
> x,y,z,x,y,z,... and so on. See the array (x,y,z) in the entry A160161:
> First differences of A160160.
>
> ==========
>
> Richard,
> In the entry A160170 a X-Toothpick is a cross with four endpoints.
>
> Best regards.
>
>
>
>
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