I wish they had chosen 2, 4, and 7. That would have made it more challenging for me. I thought the answer was the previous output x2 for sure, but since that also works and is not incredibly a difficult math problem, I feel the test doesn't really prove much about how I think.
Maybe I'm the one who misunderstood the puzzle, but isn't that basically the point? They are trying to trick you into thinking that the rule is "each number must be double the last", when it's actually much simpler. That way, if you don't try numbers that doesn't obey the rule, you won't realize that you've got the wrong theory. I can't think of any obvious incorrect rule the sequence 2, 4, 7 would fit, so people may have stumbled across the correct answer only by verifying correct sequences.
I see your point. However, I don't think that leading someone down a certain path just to pull the rug out from under their feet is the best way to prove a point. There's not a lot of self-discovery going on here. It's just that the creators would rather lead you to where they want you to go than have you lead yourself.
Maybe I'm trying to make it more complicated than it needs to be. FWIW, it was an interesting exercise and completing it made me think more critically about the project. Mission accomplished!
Except that neither 0, 0, 0 nor -1, -2, -4 worked.