What is the next number in the series. 15; 29; 56; 108; 208; ?

Question

Find the number that comes next in the following series:

3, 7, 12, 14, 16, 19, 21, 25, 30, 41, 45, 52, 54, 56, 59, 61, 65, 70, ?

Answer 1

400
.
15 * 2 - 1 = 29
29 * 2 - 2 = 56
56 * 2 - 4 = 108
108 * 2 - 8 = 208
208 * 2 - 16 = 400

Answer 2

15 x 2 - 2^0 = 29
29 x 2 - 2^1 = 56
56 x 2 - 2^2 = 108
108 x 2 - 2^3 = 208
208 x 2 - 2^4 = 400.