Fore and back

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Fore and back
2ob2o2b$2obobob$6bo$3ob3o$o6b$bobob2o$2b2ob2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ]] #C [[ GPS 2 THUMBSIZE 2 ]]
Pattern type Oscillator
Oscillator type Billiard table
Number of cells 24
Bounding box 7×7
Frequency class 30.6
Period 2
Mod 1
Heat 4
Volatility 0.15
Strict volatility 0.15
Rotor type Pole 2
Discovered by Achim Flammenkamp
Year of discovery 1994

Fore and back (or complementary blinker[1]) is a period-2 oscillator that was found by Achim Flammenkamp on July 12, 1994.[2] Its rotor is the same as the blinker.


Fore and back is about the thirty-eighth most common naturally-occurring oscillator in Achim Flammenkamp's census, being less common than boat on spark coil and block on griddle, about as common as 21P2, and more common than trans-block on long hook eating tub and trans-beacon down on long hook.[3] It is the most common oscillator that is generally agreed to be a billiard table, though some instead give this title to the more common test tube baby, which counts under a looser definition.[4]


In August 2013, a 24-glider synthesis of this oscillator was found by Martin Grant, based on a soup provided by Lewis Patterson. Several days later Mark Niemiec improved this result, having found a 20-glider synthesis.[5]

In October 2014, Tanner Jacobi found a predecessor for this pattern based on a soup from Adam P. Goucher's apgsearch script,[6] which was eventually optimized to a 6-glider synthesis[7] in November.

See also


  1. "Complementary blinker". The Life Lexicon. Stephen Silver. Retrieved on December 3, 2018.
  2. Dean Hickerson's oscillator stamp collection. Retrieved on March 14, 2020.
  3. Achim Flammenkamp (September 7, 2004). "Most seen natural occurring ash objects in Game of Life". Retrieved on January 15, 2009.
  4. Dave Greene (July 3, 2019). Re: Thread for basic questions (discussion thread) at the forums
  5. Lewis Patterson (August 4, 2013). "Synthesising Oscillators". Retrieved on September 10, 2013.
  6. Tanner Jacobi (October 15, 2014). Re: Soup search results (discussion thread) at the forums
  7. Tanner Jacobi (November 8, 2014). "Soup search results". Retrieved on November 9, 2014.

External links

  • 24P2.142 at Heinrich Koenig's Game of Life Object Catalogs