What to watch
- It takes 15 steps to return to its original phase.
- Most phases remain narrow and readable.
- The two notches control the long cycle.
Oscillators
Pentadecathlon
A slim oscillator with a much longer cycle than its size suggests.
The pentadecathlon is a compact way to show that period length can grow faster than visual complexity.
Pentadecathlon has period 15
The pentadecathlon is a compact oscillator that returns to its starting phase after 15 generations. It is useful after the blinker and pulsar because the cycle is longer while the shape remains easy to follow.
Oscillators12 cells3 x 10 boxperiod 15
- Category
- Oscillators
- Period
- 15
- Movement
- bounded
- Population
- 12 cells
- Bounding box
- 3 x 10
- Known since
- 1970
How to use it
Use it to introduce period notation beyond p2 and p3.
Open the pattern in the lab, reduce the speed, and use single-step mode when a phase change is hard to see. The green preview marks births in the next generation; red outlines mark live cells that will die.
Fast answers
Common questions about Pentadecathlon
What is the period of the pentadecathlon?
The pentadecathlon has period 15. Run 15 generations and the starting phase should return in the same place.
Why is it called pentadecathlon?
The name points to its 15-generation cycle. On this site, the useful exercise is to compare that cycle with period-2 and period-3 oscillators.
What should I compare it with?
Compare it with the blinker for period 2 and the pulsar for period 3 before moving to period-30 shuttle and gun patterns.