[seqfan] Re: Toothpick sequences (again)

Omar E. Pol info at polprimos.com
Fri Jun 5 00:25:37 CEST 2009

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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