請找出下面數列的規律
1, 2, 6, 42, 1806, ??? 解密碼，不難..動動腦
1 x 1 + 1 = 2
2 x 2 + 2 = 6
6 x 6 + 6 = 42
42 x 42 + 42 = 1806
1806 x 1806 + 1806 = 3,263,442