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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 242 |
| 5 | 4584 |
| 6 | 124936 |
| 7 | 4638360 |
| 8 | 225037200 |
| 9 | 13820428368 |
| 10 | 1048006461024 |
| 11 | 96171381464256 |
| 12 | 10503700943629824 |
| 13 | 1346451508974957696 |
| 14 | 200184649396819872768 |
| 15 | 34167655864475762390784 |
| 16 | 6635466680845611611326464 |
| 17 | 1454780635849943337186155520 |
[1,1,3,20,242,4584,124936,4638360,225037200, 13820428368,1048006461024,96171381464256, 10503700943629824,1346451508974957696, 200184649396819872768,34167655864475762390784, 6635466680845611611326464, 1454780635849943337186155520] |