Fumarole on Achim's p11 is a period 55 oscillator composed of a fumarole and Achim's p11. Although it consists of two oscillators of smaller periods (5 and 11 respectively), it is considered non-trivial because it contains a single cell that is alive in generation 31 and dead in the other 54 phases of the oscillator. In terms of its 90 cells, it was the smallest known non-trivial period 55 oscillator until the discovery of pseudo-barberpole on rattlesnake in 2016.
Generation 31 reveals the single cell that oscillates at full period (in green).
- 90P55.1 at Heinrich Koenig's Game of Life Object Catalogs