1, 2, 6, 21, 88, 445, ?

Direction: What should come in place of the question mark in each of the following number series ?

1 x 1 + 1 = 2
2 x 2 + 2 = 6
6 x 3 + 3 = 21
21 x 4 + 4 = 88
88 x 5 + 5 = 445
445 x 6 + 6 = 2676 Should come in place of '?'