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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 5 |
| 2 | 60 |
| 3 | 1020 |
| 4 | 21420 |
| 5 | 523320 |
| 6 | 14399280 |
| 7 | 437433780 |
| 8 | 14479664640 |
| 9 | 517426156800 |
| 10 | 19824547680000 |
| 11 | 810083131361280 |
| 12 | 35155640625638400 |
| 13 | 1614680474921256960 |
| 14 | 78256021787814850560 |
| 15 | 3991780109967777792000 |
| 16 | 213813097136418588641280 |
[1,5,60,1020,21420,523320,14399280,437433780, 14479664640,517426156800,19824547680000, 810083131361280,35155640625638400, 1614680474921256960,78256021787814850560, 3991780109967777792000,213813097136418588641280] |