In the following number series only one number is wrong. Find the wrong number? 2 7 30 138 524 1557

The pattern is: multiply the previous number by 4, then subtract 2, 10, 28, 74 respectively. Let's verify: 2 × 4 - 1 = 7, 7 × 4 - 2 = 26 (not 30), or alternatively: 2 × 4 - 1 = 7, 7 × 4 - 2 = 26, 26 × 4 - 10 = 94 (not 138). The actual pattern appears to be: 2, 7, 30, 138, 524, 1557 doesn't follow a single clean pattern. If we check: 7 - 2 = 5, 30 - 7 = 23, 138 - 30 = 108, 524 - 138 = 386, 1557 - 524 = 1033. These differences don't show a clear pattern. The claimed answer 138 appears to be identified as breaking a pattern that isn't immediately obvious.