Cycler
1RB0LB_1LB1LC_0RC1RA (bbch), which has period 18 and preperiod 4.A cycler is a Turing machine that eventually enters a repeating cycle. Such a Turing machine runs forever, so is a Non-halting Turing machine.
The rule for identifying cyclers is simple:
û → û
where û is any headed tape segment.