# A062833 (b-file synthesized from sequence entry)
1 2
2 2
3 6
4 16
5 120
6 360
7 5040
8 20160
9 241920
10 1814400
11 39916800
12 159667200
13 6227020800
14 43589145600
15 653837184000
16 8369115955200
17 355687428096000
18 2134124568576000
19 121645100408832000
20 810967336058880000