# A006845 (b-file synthesized from sequence entry)
1 0
2 1
3 3
4 3
5 140
6 420
7 840
8 840
9 10810800
10 75675600
11 454053600
12 2270268000
13 9081072000
14 27243216000
15 54486432000
16 54486432000
17 52401161274029568000
18 786017419110443520000
19 11004243867546209280000
20 143055170278100720640000