Instructions: In the following number series only one number is wrong. Find out the wrong number.
7, 12, 40, 222, 1742, 17390, 208608
(7-1) x 2 = 12
(12 - 2) x 4 = 40
(40 - 3) x 6 = 222
(222 - 4) x 8 = 1744 ≠ 1742
(1744 - 5) x 10 = 17390
(17390 - 6) x 12 = 208608
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