# A289830 (b-file synthesized from sequence entry)
2 -1
3 2
4 18
5 124
6 900
7 7188
8 63504
9 618336
10 6596640
11 76635360
12 963895680
13 13056819840
14 189581333760
15 2938083321600
16 48416639846400
17 845487698227200
18 15598004134809600
19 303161985274982400
20 6191998554470400000
21 132599321499875328000
22 2970952207377960960000