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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 32 |
| 5 | 180 |
| 6 | 1200 |
| 7 | 9240 |
| 8 | 80640 |
| 9 | 786240 |
| 10 | 8467200 |
| 11 | 99792000 |
| 12 | 1277337600 |
| 13 | 17643225600 |
| 14 | 261534873600 |
| 15 | 4140968832000 |
| 16 | 69742632960000 |
| 17 | 1244905998336000 |
| 18 | 23475370254336000 |
| 19 | 466306218233856000 |
| 20 | 9731608032706560000 |
[1,2,7,32,180,1200,9240,80640,786240,8467200, 99792000,1277337600,17643225600,261534873600, 4140968832000,69742632960000,1244905998336000, 23475370254336000,466306218233856000, 9731608032706560000] |