7, 12, 40, 222, 1742, 17390, 208608

The pattern of number series is as follows :
7 x 2 - 2 = 12
12 x 4 - (2 + 6) = 48 - 8 = 40
40 x 6 - (8 + 10) = 240 - 18 = 222
222 x 8 - (18 + 14) = 1776 - 32 = 1744 ≠ 1742
1744 x 10 - (32 + 18) = 17440-50=17390