This replicator for rule
B3578/S23,
was found by Dominique Giard in 1999. It replicates
itself every 12 generations, on a two-dimensional 4-unit grid.
Intriguingly, the same rule has two almost-replicators,
of periods 29 and 41, formed by placing two beehives end-to-end near
each other.
The same period 12 replicator also works in three other rules, of which
B3578/S237
has the most interesting small spaceships.
Replicators --
Cellular Automata --
D. Eppstein --
UCI Inf. & Comp. Sci.