2, 7, 30, 138, 524, 1557, 3102

(2 - 1) x 7 = 7; (7 - 2) x 6 = 30; (30 - 3) x 5 = 135; (135 - 4) x 4 = 524;
(524 - 5) x 3 = 1557; (1557 - 6) x 2 = 3102