| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 12 |
| 6 | 20 |
| 7 | 180 |
| 8 | 1260 |
| 9 | 1120 |
| 10 | 9072 |
| 11 | 90720 |
| 12 | 184800 |
| 13 | 29937600 |
| 14 | 389188800 |
| 15 | 13453440 |
| 16 | 8172964800 |
| 17 | 130767436800 |
| 18 | 15247232000 |
| 19 | 100037089152000 |
| 20 | 380140938777600 |
| 21 | 10429106688000 |
| 22 | 1451447220787200 |
| 23 | 159659194286592000 |
[1,2,3,12,20,180,1260,1120,9072,90720,184800, 29937600,389188800,13453440,8172964800, 130767436800,15247232000,100037089152000, 380140938777600,10429106688000,1451447220787200, 159659194286592000] |