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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 6 |
| 4 | 84 |
| 5 | 120 |
| 6 | 784 |
| 7 | 280 |
| 8 | 40816 |
| 9 | 13806 |
| 10 | 1361706 |
| 11 | 110990 |
| 12 | 142633176 |
| 13 | 4263454 |
| 14 | 197730660 |
| 15 | 9246172320 |
[1,4,6,84,120,784,280,40816,13806,1361706,110990, 142633176,4263454,197730660,9246172320] |