n | a(n) |
---|---|
0 | 1 |
1 | 4 |
2 | 20 |
3 | 168 |
4 | 1200 |
5 | 7600 |
6 | 43200 |
7 | 407680 |
8 | 2712832 |
9 | 19707408 |
10 | 112560000 |
11 | 945677920 |
12 | 6768230400 |
13 | 47530457728 |
14 | 271289229120 |
15 | 2096760960000 |
16 | 16569393144832 |
17 | 116315256993600 |
18 | 597938524646400 |
19 | 5699431359135360 |
20 | 38890647857280000 |
21 | 270061302781670400 |
[1,4,20,168,1200,7600,43200,407680,2712832, 19707408,112560000,945677920,6768230400, 47530457728,271289229120,2096760960000, 16569393144832,116315256993600,597938524646400, 5699431359135360,38890647857280000, 270061302781670400] |