# A121639 (b-file synthesized from sequence entry)
1 0
2 1
3 5
4 25
5 147
6 996
7 7668
8 66264
9 635976
10 6717600
11 77482080
12 969338880
13 13076778240
14 189261999360
15 2925629280000
16 48111515827200
17 838731380659200
18 15451544605593600
19 299960798422118400
20 6120505381423104000