Pentadecathlon

Pentadecathlon
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Pattern type	Oscillator
Number of cells	12
Bounding box	16×9
Frequency class	18.6
Period	15
Mod	15
Heat	22.4
Volatility	1.00
Strict volatility	1.00
Discovered by	John Conway
Year of discovery	1970
Rules Outer-totalistic rules B3/S23 – B3/S023 Important rules Conway Life # of rules 21 = 2 Isotropic rules B3-ckny/S23aeiy – B2n34-aeiw5-e6-ik7c/S0234cjkqyz5-aiqy6-c
Glider synthesis Fewest gliders 3 Catagolue-generated RLE pentadecathlon_synth.rle Uploaded synthesis RLE pentadecathlon_synth.rle
Pattern files Plaintext pentadecathlon.cells RLE pentadecathlon.rle
Identifiers apgcode xp15_4r4z4r4 Pentadecathlon ID 12P15.1

Pentadecathlon (or PD; plural pentadecathlons) is a period-15 oscillator that was found in 1970 by John Conway while tracking the history of short rows of cells (see one-cell-thick pattern); indeed, an orthogonal row of 10 cells evolves into this object. It is the only known oscillator that is a polyomino in more than one phase (besides the blinker).

Commonness

Pentadecathlon is the most natural oscillator of period greater than 3 (and indeed, the second most natural oscillator of period greater than 2) in Achim Flammenkamp's census. In fact, it is the fifth or sixth most common oscillator overall in this census, being about as frequent as the clock, but much less frequent than the blinker, toad, beacon or pulsar. It is also the most common oscillator with a volatility of 1. The pentadecathlon is also the fifty-second most common object on Adam P. Goucher's Catagolue and by far the most common period 15 oscillator, with all other natural oscillators of that period featuring it combined with some other object.

Uses of the pentadecathlon

The pentadecathlon is so called because it has a period of 15 generations. This, being a factor of 30, means that it can be elegantly used in combination with period 30 devices (based on the queen bee shuttle). Firstly, it can reflect a glider 180° as in p60 glider shuttle, and a pair of perpendicular pentadecathlons can rotate a glider 90°.

Hassling capabilities

The pentadecathlon is classified as a pulsating oscillator, since it undulates throughout its cycle. During this process, the pentadecathlon throws off multiple accessible sparks. More specifically, the oscillator produces horizontal T-nose sparks, horizontal V sparks and vertical domino sparks. Two copies of these domino sparks can be used to hassle toads in two distinct ways. The V sparks elegantly convert blocks into gliders, which forms the basis of the p30 *WSS => glider converter and aforementioned glider reflectors. This property is also exploited in numerous oscillators.

Synthesis

On April 11, 1997, Heinrich Koenig found a three-glider collision that produced a clean pentadecathlon. This was a surprising result at the time. Four-glider pentadecathlon recipes had been known and used for many years, so this was an unlooked-for improvement, very similar to Luka Okanishi's discovery of a three-glider synthesis of a switch engine almost twenty years later. This also makes the pentadecathlon the rarest object in Catagolue for which a 3-glider synthesis is known.

Other rules

• In EightLife, it still functions as a period 15 oscillator, but it generates extra internal sparks.

See also

• Jolson
• Karel's p15
• Loaflipflop
• Mold on pentadecathlon
• Pentadecathlon on 37P7.1
• Pentadecathlon on thumb 1
• PD-pair reflector

External links

• Pentadecathlon at the Life Lexicon

• Pentadecathlon at Adam P. Goucher's Catagolue

• 12P15.1 at Heinrich Koenig's Game of Life Object Catalogs