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A194700 D-toothpick sequence of the third kind (see Comments lines for definition). 15
0, 1, 5, 13, 29, 51, 75, 97, 137, 177, 209, 241, 297, 371, 467, 533 (list; graph; refs; listen; history; text; internal format)



This is a cellular automaton of forking paths to 135 degrees which uses elements of three sizes: toothpicks of length 1, D-toothpicks of length 2^(1/2) and D-toothpicks of length 2^(1/2)/2. Toothpicks are placed in horizontal or vertical direction. D-toothpicks are placed in diagonal direction. Toothpicks and D-toothpicks are connected by their endpoints.

On the infinite square grid we start with no elements.

At stage 1, place a single D-toothpick on the paper, in diagonal direction.

The rule for adding new elements is as follows. Each exposed endpoint of the elements of the old generation must be touched by the two endpoints of two elements of the new generation such that the angle between the old element and each new element is equal to 135 degrees. Intersections and overlapping are prohibited.

This toothpick structure is very similar to A194270, but here there are no toothpicks endpoints that remain exposed forever.


Table of n, a(n) for n=0..15.

David Applegate, The movie version

N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS

Index entries for sequences related to toothpick sequences


Cf. A139250, A194270.

Sequence in context: A129371 A212008 A194270 * A220500 A130230 A106931

Adjacent sequences:  A194697 A194698 A194699 * A194701 A194702 A194703




Omar E. Pol, Sep 02 2011



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Last modified January 28 00:32 EST 2020. Contains 331313 sequences. (Running on oeis4.)