Look at this series: 53, 53, 40, 40, 27, 27, ... What number should come next?

Look at this series: 53, 53, 40, 40, 27, 27, ... What number should come next?

2) 2, 3, 6, 15, ?, 123

3) 6, 13, 28, 59, ?, 249.

4) Which of the following will come in place of the question mark (?) in the following sequence?
PRODUCTIVITY, RODUCTIVIT, ODUCTIVI, ?

5) Look at this series: 53, 53, 40, 40, 27, 27, ... What number should come next?