x = 23, y = 23, rule = B36/S23
o$3o$3bo$bboo3$10b3o$9bobbo$8bo3bo$8bobbo$8b3o9$19boo$19bobo$21bo$21b
oo!
This is a period 48 replicator based oscillator.
This works by using two eaters to constrain a replicator.  Higher period
oscillators with periods which are multiples of 48 can be made by moving
the eaters further apart.
Dean Hickerson, 1994