3, 7, 15, 39, 63, 127, 255, 511

Go on dividing by 4 to get the next number.

So, 200 is wrong.

Each even term of the series is obtained by multiplying the previous term by 2.

2^nd term = (1^st term) x 2 = 6 x 2 = 12

4^th term = (3^rd term) x 2 = 48 x 2 = 96.

6^th term = (5^th term) x 2 = 384 x 2 =768.

∴ 4^th term should be 96 instead of 100.

A x 2 + 1, B x 3 + 1, C x 2 + 1, D x 3 + 1 and so on.

So, 356 is wrong.

Go on adding 7, 9, 11, 13, 15, 17 respectively to obtain the next number.

So, 33 is wrong. It must be 35

Go on subtracting 24, 21, 18, 15, 12, 9 from the numbers to get the next number.

190 - 24 = 166
166 - 21 = 145
145 - 18 = 127 [Here, 128 is placed instead of 127]
127 - 15 = 112
112 - 12 = 100 ... and so on.

Therefore, 128 is wrong.

Go on adding 7, 9, 11, 13, 15, 17, 19 respectively to obtain the next number.

So, 135 is wrong.

2^nd term = (1^st term) x 1 + 1 = 15 x 1 + 1 = 16.

3^rd term = (2^nd term) x 2 + 2 = 16 x 2 + 2 = 34.

4^th term = (3^th term) x 3 + 3 = 34 x 3 + 3 = 105.

5^th term = (4^th term) x 4 + 4 = 105 x 4 + 4 = 424

6^th term = (5^th term) x 5 + 5 = 424 x 5 + 5 = 2125

∴ 6^th term should 2125 instead of 2124.

2^nd term = (1^st term) x 3 - 4 = 10 x 3 - 4 = 26.

3^rd term = (2^nd term) x 3 - 4 = 26 x 3 - 4 = 74.

4^th term = (3^th term) x 3 - 4 = 74 x 3 - 4 = 218.

5^th term = (4^th term) x 3 - 4 = 218 x 3 - 4 = 650.

∴ 5^th term must be 650 instead of 654.

Go on dividing by 6, 5, 4, 3, 2, 1 respectively to obtain the next number.

Clearly, 92 is wrong.

Go on multiplying the number by 2 and adding 1 to it to get the next number.

So, 27 is wrong.