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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | 1080 |
| 7 | 6300 |
| 8 | 30240 |
| 9 | 130032 |
| 10 | 18665640 |
| 11 | 660623700 |
| 12 | 13658934960 |
| 13 | 212523761736 |
| 14 | 2764009560312 |
| 15 | 77520900775500 |
| 16 | 4099129923470400 |
| 17 | 172565711699473632 |
| 18 | 5540231695274913096 |
| 19 | 145530177163066645380 |
| 20 | 3989207890319572270800 |
| 21 | 168566608848038865057720 |
[1,0,0,0,0,120,1080,6300,30240,130032,18665640, 660623700,13658934960,212523761736,2764009560312, 77520900775500,4099129923470400, 172565711699473632,5540231695274913096, 145530177163066645380,3989207890319572270800, 168566608848038865057720] |