1, 5, 5, 9, 7, 11, 11, 15, 12, 17

1.	1, 5, 5, 9, 7, 11, 11, 15, 12, 17
Answer» The given sequence is a combination of two series: I. 1, 5, 7, 11, 12 and II. 5, 9, 11, 15, 17 The pattern in both I and II is + 4, + 2, + 4, + 2. So, 12 is wrong and must be replaced by (11 + 2) i.e. 13.

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