what is rule 146??

Rule 146 is an elementary class 3 cellular automaton rule. I think rule 146 is interesting because although its behavior seems largely random:

An
An evolution of rule 146 from random initial conditions.

... it may also be programmable via particle structures hidden in the evolution (highlighted here in red):

Single
Single particle propagating in rule 146.

If rule 146 turns out to be generally programmable (i.e. if it could emulate a universal Turing machine), that would provide some (circumstantial) evidence that class 3 (random-looking) systems are generally programmable. See here for more on why this is actually kind of a deep problem.