# A009328 (b-file synthesized from sequence entry)
0 0
1 1
2 -1
3 2
4 -6
5 16
6 -72
7 328
8 -1904
9 12160
10 -89344
11 721280
12 -6445824
13 62638720
14 -660602880
15 7495723264
16 -91175548928
17 1182630301696
18 -16301080281088
19 237887012458496
20 -3664597991424000
21 59422015832915968