# A204428 (b-file synthesized from sequence entry)
1 2
2 4
3 9
4 40
5 192
6 1032
7 7824
8 62496
9 530712
10 5619456
11 61710336
12 707802624
13 9591229440
14 133983590400
15 1938416832000
16 32061464064000
17 544216485888000
18 9509523337728000
19 185772505605120000
20 3711395156281344000