"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." If you love solving riddles, unlocking mysteries, or completing any other brain-boosting activity, puzzle ...

A number sequence has gone viral on the internet this week, reading: 2, 6, 12, 20, 30, ?. At first glance, it looks easy, but once people start solving it, they realize spotting the pattern is not so ...