x = 17, y = 15, rule = B3678/S34678
8bo$$8bo$$8bo$3b5ob5o$b15o$b7ob7o$17o$oob5ob5oboo$8bo$$8bo$$8bo!
Period 8 spark oscillator.
The spark can be made into two bits by duplicating the column containing
the spark.
Dean Hickerson, April 1997
