Directions: Identify the wrong term in the given number series.

15, 31, 64, 135, 266, 537, 1080

The correct answer is 135.

To identify the wrong term in the given number series, let us analyze the mathematical pattern connecting consecutive terms:

15, 31, 64, 135, 266, 537, 1080

By observing the progression, each term is obtained by multiplying the previous term by 2 and then adding consecutive integers starting from 1:

First term: 15

$15\times 2+1=31$

$31\times 2+2=64$

$64\times 2+3=131$

According to this rule, the fourth term should be 131 instead of 135.

Let us verify if the remaining terms follow the exact same rule using the correct fourth term (131):

$131\times 2+4=266$

$266\times 2+5=537$

$537\times 2+6=1080$

Since all subsequent terms match the series perfectly when 135 is replaced by 131, the wrong term in the series is 135.