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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 14 |
| 5 | 64 |
| 6 | 426 |
| 7 | 2790 |
| 8 | 24024 |
| 9 | 229080 |
| 10 | 2399760 |
| 11 | 25022880 |
| 12 | 312273360 |
| 13 | 3884393520 |
| 14 | 56255149440 |
| 15 | 869007242880 |
| 16 | 14266826784000 |
| 17 | 233845982899200 |
| 18 | 4309095479673600 |
| 19 | 79300508301907200 |
| 20 | 1620482929875532800 |
| 21 | 34699018357638835200 |
| 22 | 777011144137311283200 |
[1,1,1,3,14,64,426,2790,24024,229080,2399760, 25022880,312273360,3884393520,56255149440, 869007242880,14266826784000,233845982899200, 4309095479673600,79300508301907200, 1620482929875532800,34699018357638835200, 777011144137311283200] |