The pseudo-barberpole (or Achim's p5) is a period 5 oscillator that was found by Achim Flammenkamp on August 22, 1994. With a minimum population of 15 cells, it is the smallest known period 5 oscillator, followed by octagon 2 with 16 cells. On October 23, 2002 Gabriel Nivasch found a period 5 oscillator that consists of four radially symmetrically arranged halves of the pseudo-barberpole.
Goldtiger997 found a 16-glider synthesis based on a sample soup from Adam P. Goucher's Catagolue on April 22, 2017. Martin Grant found an unrelated 13-glider synthesis that can also act as a component on June 20, 2018.
A radially symmetric relative of the pseudo-barberpoleRLE: here
- 15P5.1 at Heinrich Koenig's Game of Life Object Catalogs