[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:
- 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.
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