# A002497 (b-file synthesized from sequence entry)
1 3
2 12
3 60
4 420
5 4620
6 60060
7 180180
8 360360
9 6126120
10 116396280
11 2677114440
12 77636318760
13 2406725881560
14 89048857617720
15 3651003162326520
16 156993135980040360
17 313986271960080720
18 14757354782123793840
19 14757354782123793840
20 782139803452561073520
21 46146248403701103337680