I got it right but partly because considering the context in which the question was asked I figured that simply doubling each previous number seemed too obvious. It gave us that 2,4,8 was true. I tried 1,2,4 and it said yes. I tried 4,8,16 and it said yes. Then I tried 2,4,9 and it said yes. Then I tried 100, 1000, 1001 and it said yes.
I don't know why they used this for an example of confirmation bias though. I think there are lots better out there.