mark9207 — "If 102 were 108, 78 would fit into the pattern. As it is, I cannot pick up on a pattern. I look forward to the explanation."Slide cursor for another hint ➔ The numbers 4, 6, 12, 18, 30, 42, 60, 72, 102, 108, 138, ... are unique in the "immediate company they keep." This problem is more difficult than the average puzzler.