Mold on fumarole is a period 20 oscillator composed of a mold and a fumarole. In terms of its 30 cells, it is the smallest known period 20 oscillator.
Despite being composed of two oscillators of smaller period (4 and 5 respectively), it is considered non-trivial because it has a single cell that is alive in generation 1 and is dead in its other 19 phases.
Generation 1 reveals the single cell with period 20 (in green)
- ↑ Jason Summers' all-osc pattern collection. Retrieved on April 17, 2009.