What number would replace the question mark in the series given below? 1, 6, 14, 40, 108, 296, 808, ?

The next term is 2208.

Each term equals twice the sum of the two preceding terms.

Check: 2 x (6 + 1) = 14 and 2 x (14 + 6) = 40.

Also 2 x (296 + 108) = 808 confirms the rule.

So next = 2 x (808 + 296) = 2 x 1104 = 2208.