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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 38 |
| 4 | 656 |
| 5 | 17776 |
| 6 | 695104 |
| 7 | 37049648 |
| 8 | 2581673216 |
| 9 | 227817246976 |
| 10 | 24829660693504 |
| 11 | 3275474443371008 |
| 12 | 514345822537650176 |
| 13 | 94806411271686270976 |
| 14 | 20269838348763427323904 |
| 15 | 4975513260049237751994368 |
[1,1,4,38,656,17776,695104,37049648,2581673216, 227817246976,24829660693504,3275474443371008, 514345822537650176,94806411271686270976, 20269838348763427323904,4975513260049237751994368] |