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A187210 Q-toothpick sequence (see Comments for precise definition). 29
0, 1, 5, 12, 24, 46, 66, 88, 128, 182, 222, 244, 284, 338, 394, 464, 584, 718, 790, 812, 852, 906, 962, 1032, 1152, 1286, 1374, 1444, 1564, 1714, 1882, 2128, 2488, 2814, 2950, 2972, 3012, 3066, 3122, 3192, 3312, 3446, 3534, 3604, 3724, 3874, 4042, 4288, 4648, 4974, 5126, 5196, 5316, 5466, 5634, 5880, 6240, 6582, 6814, 7060, 7436, 7890, 8458, 9296, 10328 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

We define a “Q-toothpick” to be a quarter-circle. The length of a Q-toothpick is equal to Pi/2 = 1.570796...

In order to construct this sequence we use the following rules:

- Each new Q-toothpick must lie on the square grid (or circular grid) such that the Q-toothpick endpoints coincide with two opposite vertices of an unit square.

- Each exposed endpoint of the Q-toothpicks of the old generation must be touched by the endpoints of two q-toothpicks of new generation without creating a corner or vertex between these three arcs such that the couple of new Q-toothpicks should look like a "gullwing".

Note that in the Q-toothpick structure sometimes there is also an internal growth of the Q-toothpicks.

The sequence gives the number of Q-toothpicks in the structure after n stages. A187211 (the first differences) gives the number of Q-toothpicks added at n-th stage.

Note that the structure of the Q-toothpick cellular automaton contains distinct types of geometrical figures, for example: circles, diamonds, hearts, heads or flower vases (which appears only on the main diagonal) and also an infinity family of objects (blobs) where every object is a closed region which contains 2^k virtual circles with radius 1 and 2^k-1 virtual diamonds, for example: a 2x2-object is a closed region which contains exactly four virtual circles and three virtual diamonds, a 2x4-object is a closed region which contains exactly 8 virtual circles and 7 virtual diamonds, etc. Note that a "heart" can be considered a 1x2-object which contains two virtual circles and a virtual diamond. What is the better name for these figures? Note that there is a correspondence between this last family of objects and the squares and rectangles of the hidden crosses in the toothpick structure of A139250. For more information about the connection with the toothpick sequence see A139250, A160164 and A187220.

It appears that the number of hearts present in the n-th generation equals the number of rectangles of area = 2 present in the (n - 2)nd generation of the toothpick structure of A139250, assuming the toothpicks have length 2, if n >= 3 (See also A188346 and A211008). - Omar E. Pol, Sep 30 2012

From Omar E. Pol, Jan 23 2016: (Start)

Consider the initial Q-toothpick with the virtual center at (0,0) and its endpoints at (0,1) and (1,0).

If n is a power of 2 plus 2 and n >> 1 then the structure of this C.A. essentially looks like a square which contains four parts (or sectors) as follows:

1) NW quadrant, but whose origin is at (-1,1). In this quadrant the number of Q-toothpicks after n generations equals the number of toothpicks in the toothpick structure of A139250 after n-2 generations, if n >= 2. Note that here the toothpick sequence A139250 is represented with Q-toothpicks arranged in an asymmetric structure.

2) SE quadrant, but whose origin is at (1,-1). This quadrant is a reflected copy of the NW quadrant, hence the number of Q-toothpicks after n generations equals A139250(n-2), n >= 2, the same as in the NW quadrant.

3) SW quadrant, but with the origin in the first quadrant at (1,1). In this quadrant the number of Q-toothpicks after n generations is 1 + A267694(n-1), n >= 1.

4) NE quasi-quadrant. In this sector the number of Q-toothpicks after n-generations is A267698(n-2) - 2, if n >= 6. (End)

After the first few generations the behavior is similar to the Gullwing cellular automaton of A187220, but the growth is faster than A187220 and thus it's much faster than A139250. For an animation see Applegate's The movie version in the Links section. - Omar E. Pol, Sep 13 2016

REFERENCES

A. Adamatzky and G. J. Martinez, Designing Beauty: The Art of Cellular Automata, Springer, 2016, pages 59, 62 (note that the Q-toothpick cellular automaton is erroneously attributed to Nathaniel Johnston).

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 0..177

David Applegate, The movie version

David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata

Nathaniel Johnston, Animation of the first 19 generations

Nathaniel Johnston, Illustration of a(5) = 46, “Front Matter” 2015. The College Mathematics Journal 46 (1). Mathematical Association of America: 1-1. doi:10.4169/college.math.j.46.1.fm.

Nathaniel Johnston, The Q-Toothpick Cellular Automaton

Nathaniel Johnston, The Q-Toothpick post in ConwayLife.com

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

FORMULA

a(0)=0; a(1)=1; a(n) = 2*A139250(n-2) + A267698(n-2) + A267694(n-1) + m, where m = 3 if 2<=n<=5 and m = -1 if n>=6 (Note that 2*A139250(n-2) can be replaced with A160164(n-2)). - Omar E. Pol, Jan 23 2016

a(n) = A187220(n-1) + A267698(n-2) + A267694(n-1) + m, where m = 2 if 2<=n<=5 and m = -2 if n>=6. - Omar E. Pol, Sep 13 2016

EXAMPLE

From Omar E. Pol, Apr 02 2016: (Start)

Examples that are related to the toothpick sequence A139250 (see the first formula):

For n = 5 we have that A139250(5-2) = 7, A267698(5-2) = 13, A267694(5-1) = 16 and m = 3, so a(5) = 2*7 + 13 + 16 + 3 = 46.

For n = 6 we have that A139250(6-2) = 11, A267698(6-2) = 25, A267694(6-1) = 20 and m = -1, so a(6) = 2*11 + 25 + 20 - 1 = 66. (End)

From Omar E. Pol, Sep 13 2016: (Start)

Examples that are related to the Gullwing sequence A187220 (see the second formula):

For n = 5 we have that A187220(5-1) = 15, A267698(5-2) = 13, A267694(5-1) = 16 and m = 2, so a(5) = 15 + 13 + 16 + 2 = 46.

For n = 6 we have that A187220(6-1) = 23, A267698(6-2) = 25, A267694(6-1) = 20 and m = -2, so a(6) = 23 + 25 + 20 - 2 = 66. (End)

CROSSREFS

Cf. A139250, A160164, A187211, A187212, A187220, A188344, A188345, A188346, A267694, A267698.

Sequence in context: A101425 A191831 A188182 * A126880 A108314 A079425

Adjacent sequences:  A187207 A187208 A187209 * A187211 A187212 A187213

KEYWORD

nonn

AUTHOR

Omar E. Pol, Mar 07 2011

EXTENSIONS

Terms a(8) and beyond from Nathaniel Johnston, Mar 26 2011

Comments edited by Omar E. Pol, Mar 28 2011

Second rule clarified by Omar E. Pol, Apr 06 2011

STATUS

approved

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Last modified August 18 14:09 EDT 2017. Contains 290720 sequences.