Forumula : answer x 7 ( -2 per step ) + aswer/2

Step 1

0x

1x

2x

3x

4x

= 0

Step 2

1x

2x

3x

4x

5x

= 120

Step 3

2x

3x

4x

5x

6x

= 720

Step 4

3x

4x

5x

6x

7x

= 2520

Step 5

4x

5x

6x

7x

8x

= 6720

Step 6

5x

6x

7x

8x

9x

= 15120