What number would replace the question mark (?) in the series given below? 1, 6, 18, 44, 98, 208, 430, ?

The number that fits is 876.

Each term follows next = term x 2 + an even number that grows by 2.

1 x 2 + 4 = 6, 6 x 2 + 6 = 18, 18 x 2 + 8 = 44.

44 x 2 + 10 = 98, 98 x 2 + 12 = 208, 208 x 2 + 14 = 430.

430 x 2 + 16 = 876.