[seqfan] Re: Toothpick sequences (again)
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
On Thu, Jun 4, 2009 at 3:25 PM, Omar E. Pol<info at polprimos.com> wrote:
> 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!.
> About the toothpick sequence A139250:
> For the area, see A159786.
> For the number of cells, see A147614.
> For the number of rectangles, see A160124.
> 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.
> In the entry A160170 a X-Toothpick is a cross with four endpoints.
> Best regards.
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