Which of the following is not an innovative technique

2, 6, ?,  20, 30, 42

15, 31, 67, 131, ?, 375

18, 21, 45, 138, 555, ?

178        168       148      ?      78       28

Which of the following number will replace the question mark (?) and complete the given number series?

4, 5, 12, 39, 160, ?

106, 124, 88, 142, ?, 160

18, 30, 54, 90, 138, ?

What will come in place of the question mark (?) in the following series?

130, 158, 214, 298, ?, 550

Find the missing number in the given number series.

3, 7, 18, 38, 69, ?