Rule 37R

Complicated structures are fairly easy to get with this rule. The initial condition {1, 0, 1} with all cells 0 on the previous step yields a structure that repeats but only every 666 steps. The initial condition {{0, 1, 1}, {1, 0, 0}} yields a pattern that grows sporadically for 3774 steps, then breaks into two repetitive structures. The typical background repeats every 3 steps.