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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 6 |
| 4 | 36 |
| 5 | 540 |
| 6 | 8400 |
| 7 | 169680 |
| 8 | 3966480 |
| 9 | 107518320 |
| 10 | 3295283040 |
| 11 | 112888369440 |
| 12 | 4272403544640 |
| 13 | 177061349424960 |
| 14 | 7974538914101760 |
| 15 | 387840385867334400 |
| 16 | 20257533315635616000 |
| 17 | 1130954856127948051200 |
| 18 | 67208532822729871372800 |
| 19 | 4235759061057115720128000 |
[1,0,6,36,540,8400,169680,3966480,107518320, 3295283040,112888369440,4272403544640, 177061349424960,7974538914101760, 387840385867334400,20257533315635616000, 1130954856127948051200,67208532822729871372800, 4235759061057115720128000] |