Nine distinct light bulbs are placed in a circle. Each light bulb can be on or off. In order to properly light up the room, in each group of four adjacent light bulbs, at least one must be turned on. How many such configurations are there?
Nine distinct light bulbs are placed in a circle. Each light bulb can be on or off. In order to properly light up the room, in each group of four adjacent light bulbs, at least one must be turned on. How many such configurations are there?