# A013249 (b-file synthesized from sequence entry)
0 0
1 0
2 -1
3 4
4 -6
5 0
6 -90
7 600
8 6440
9 -96320
10 282240
11 -28800
12 63518400
13 -658944000
14 -11371279920
15 255692673600
16 -859133808000
17 9642264652800
18 -1104139083715200
19 14885344037491200
20 258279234868512000