Toothpick sequence

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The first three steps of the toothpick sequence and its emulation by a cellular automaton with the Margolus neighborhood Margolus toothpick animated.gif
The first three steps of the toothpick sequence and its emulation by a cellular automaton with the Margolus neighborhood
The 89th stage of the sequence, one of the stages at which T(n)/n is near its minimum Toothpick 89.svg
The 89th stage of the sequence, one of the stages at which T(n)/n is near its minimum

In geometry, the toothpick sequence is a sequence of 2-dimensional patterns which can be formed by repeatedly adding line segments ("toothpicks") to the previous pattern in the sequence.

Geometry branch of mathematics that measures the shape, size and position of objects

Geometry is a branch of mathematics concerned with questions of shape, size, relative position of figures, and the properties of space. A mathematician who works in the field of geometry is called a geometer.

The first stage of the design is a single "toothpick", or line segment. Each stage after the first is formed by taking the previous design and, for every exposed toothpick end, placing another toothpick centered at a right angle on that end. [1]

This process results in a pattern of growth in which the number of segments at stage n oscillates with a fractal pattern between 0.45n2 and 0.67n2. If T(n) denotes the number of segments at stage n, then values of n for which T(n)/n2 is near its maximum occur when n is near a power of two, while the values for which it is near its minimum occur near numbers that are approximately 1.43 times a power of two. [2] The structure of stages in the toothpick sequence often resemble the T-square fractal, or the arrangement of cells in the Ulam–Warburton cellular automaton. [1]

Fractal A self-similar pattern or set

In mathematics, a fractal is a subset of a Euclidean space for which the Hausdorff dimension strictly exceeds the topological dimension. Fractals tend to appear nearly the same at different levels, as is illustrated here in the successively small magnifications of the Mandelbrot set; Because of this, fractals are encountered ubiquitously in nature. Fractals exhibit similar patterns at increasingly small scales called self similarity, also known as expanding symmetry or unfolding symmetry; If this replication is exactly the same at every scale, as in the Menger sponge, it is called affine self-similar.

In mathematics, the T-square is a two-dimensional fractal. It has a boundary of infinite length bounding a finite area. Its name comes from the drawing instrument known as a T-square.

Ulam–Warburton automaton

The Ulam–Warburton cellular automaton (UWCA) is a 2-dimensional fractal pattern that grows on a regular grid of cells consisting of squares. Starting with one square initially ON and all others OFF, successive iterations are generated by turning ON all squares that share precisely one edge with an ON square.This is the von Neumann neighborhood. The automaton is named after the Polish-American mathematician and scientist Stanislaw Ulam and the Scottish engineer, inventor and amateur mathematician Mike Warburton who was educated at George Heriot's School in Edinburgh.

All of the bounded regions surrounded by toothpicks in the pattern, but not themselves crossed by toothpicks, must be squares or rectangles. [1] It has been conjectured that every open rectangle in the toothpick pattern (that is, a rectangle that is completely surrounded by toothpicks, but has no toothpick crossing its interior) has side lengths and areas that are powers of two, with one of the side lengths being at most two. [3]

Conjecture proposition in mathematics that is unproven

In mathematics, a conjecture is a conclusion or proposition based on incomplete information, for which no proof has been found. Conjectures such as the Riemann hypothesis or Fermat's Last Theorem have shaped much of mathematical history as new areas of mathematics are developed in order to prove them.

Power of two two raised to an integer power

In mathematics, a power of two is a number of the form 2n where n is an integer, that is, the result of exponentiation with number two as the base and integer n as the exponent.

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References

  1. 1 2 3 Applegate, David; Pol, Omar E.; Sloane, N. J. A. (2010). "The toothpick sequence and other sequences from cellular automata". Proceedings of the Forty-First Southeastern International Conference on Combinatorics, Graph Theory and Computing. Congressus Numerantium. 206. pp. 157–191. arXiv: 1004.3036 . Bibcode:2010arXiv1004.3036A. MR   2762248.
  2. Cipra, Barry A. (2010). "What Comes Next?". Science. AAAS. 327: 943. doi:10.1126/science.327.5968.943.
  3. Sloane, N.J.A. (ed.). "SequenceA139250(Toothpick sequence)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.

Brian Hayes is an American scientist, columnist and author.