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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 0 |
| 5 | 60 |
| 6 | 2520 |
| 7 | 840 |
| 8 | 181440 |
| 9 | 6063120 |
| 10 | 11642400 |
| 11 | 1437337440 |
| 12 | 44626982400 |
| 13 | 254278664640 |
| 14 | 24575197046400 |
| 15 | 756010400745600 |
| 16 | 9284429893939200 |
| 17 | 784770965801222400 |
| 18 | 25067890370095372800 |
| 19 | 541810656586725926400 |
| 20 | 42351473267452597248000 |
| 21 | 1461224653966598493772800 |
| 22 | 48020130717168717960652800 |
[1,0,0,6,0,60,2520,840,181440,6063120,11642400, 1437337440,44626982400,254278664640, 24575197046400,756010400745600,9284429893939200, 784770965801222400,25067890370095372800, 541810656586725926400,42351473267452597248000, 1461224653966598493772800, 48020130717168717960652800] |