28P7.1 is an unnamed period-7 oscillator discovered by Dean Hickerson on November 1, 1998. In terms of its 28 cells, it is tied with oscillators burloaferimeter, 28P7.2, and 28P7.3 as the smallest known period 7 oscillator.
Using a sufficiently accessible dot spark, this oscillator can be phase shifted one generation backwards. The period of the resulting oscillator is the smallest number of the form 7n+1 which is also a multiple of the spark period.
- 28P7.1 at Heinrich Koenig's Game of Life Object Catalogs