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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 28 |
| 5 | 204 |
| 6 | 2000 |
| 7 | 24030 |
| 8 | 344652 |
| 9 | 5740560 |
| 10 | 109023264 |
| 11 | 2326287600 |
| 12 | 55117624320 |
| 13 | 1436196484800 |
| 14 | 40826537706240 |
| 15 | 1257537996514800 |
| 16 | 41726938979325600 |
| 17 | 1484001670159008000 |
| 18 | 56319120817785745920 |
| 19 | 2271900191107266720000 |
| 20 | 97080540724816485258240 |
[1,2,5,28,204,2000,24030,344652,5740560,109023264, 2326287600,55117624320,1436196484800, 40826537706240,1257537996514800,41726938979325600, 1484001670159008000,56319120817785745920, 2271900191107266720000,97080540724816485258240] |