Find out the right number for question (?) mark in the following question:

$1, 2, 6, 15, 31, 56, ?$

Find out the right number for question mark (?) in the following question:

$1, 4, 27, 256, 3125, ?$

$1, 2, 4, 8, 16, 32, ?$

Find the number that comes in the place of (?) in the given series:

$2, 5, 9,19, 37, ?$

Find out the term in the place of the question mark ($?$).

$\frac{4}{9}, \frac{9}{20}, ? , \frac{39}{86}$