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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 18 |
| 4 | 456 |
| 5 | 13560 |
| 6 | 510480 |
| 7 | 25326000 |
| 8 | 1624815360 |
| 9 | 131671008000 |
| 10 | 13168037030400 |
| 11 | 1593348686899200 |
| 12 | 229442495919436800 |
| 13 | 38775787414703539200 |
| 14 | 7600054444782928128000 |
| 15 | 1710012252494048735232000 |
[0,0,18,456,13560,510480,25326000,1624815360, 131671008000,13168037030400,1593348686899200, 229442495919436800,38775787414703539200, 7600054444782928128000,1710012252494048735232000] |