Puzzle #255: How long will it take for all eight bulbs to be lit up?

#255 Final light bulb moment

set by Zoe, Rob, Brian and friends

The Headscratcher team sat brainstorming ideas for the final problem in this iteration of New Scientist‘s puzzle column. “We should probably give it a seasonal flavour,” said Brian. “Something about festive decorations?” said Rob.

“We could base it on the eight lights on my mantelpiece,” said Zoe. “I’ve programmed the one on the left to blink on and off every second. Each of the other lights also switches state every second, but only when all the lights to the left of that light are on.”

“Sounds complicated,” said Alison. “Not really,” said Zoe.…