Find the wrong number in the following sequence 2, -7, 10, -65, 29, -215, 50, -342

Find the wrong number in the following sequence 2, -7, 10, -65, 26, -215, 50, -342

Options:

A) -7
B) 26
C) -65
D) -215

Clue:
1) Addition of previous number with multiples of X
2) -(X^3 – 1)

Answer

C) -65 Explanation: Split number sequence into 2 series Series 1: 2, 10, 26, 50 Series 2: -7, -65, -215, -342 Series 1 logic: The series is made up of addition of the previous term with multiples of 8. First term: 2 + 8(0) = 2 Second term: First term + 8(1) = 2+8 =10 Third term = Second term + 8(2) = 10 + 16 = 26 Fourth term : Third term + 8(3) = 26 + 24 = 50 Series 2 logic: The series is made with a pattern (-X^3-1) which translates to -2^3 – 1 = 7 -4^3 – 1 = 63 -6^3 – 1 = 215 -7^3 – 1 = 342 Hence, in the given series 65 is wrong, it should be 63

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