# A155519 (b-file synthesized from sequence entry)
1 1
2 2
3 4
4 16
5 72
6 432
7 2880
8 23040
9 201600
10 2016000
11 21772800
12 261273600
13 3353011200
14 46942156800
15 697426329600
16 11158821273600
17 188305108992000
18 3389491961856000
19 64023737057280000
20 1280474741145600000