Puzzler of 01/21/2012: What is X in the series 4, 6, 12, 18, 30, 42, 60, X, 102, ...?

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mark9207 — '"I could see this being a question on one of those tests, of course with only one correct answer and only one correct explanation."
If I remember correctly, my BlueBook exam at the University of Chicago, Spring 1975, Mathematics Dept. asked the questions:
  • why is each number a product of 6?
  • what is it a product of in a hexidecimal system?
All the entries after yours were copied from Google searches and the copiers don't know crap about what they are posting. They are just a bunch of math wannabes.

Disgusting. It’s the last time I submit an answer to a puzzler. I’ll let the pseudo math-gurus answer first.