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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 5 |
| 3 | 28 |
| 4 | 168 |
| 5 | 1056 |
| 6 | 6864 |
| 7 | 45760 |
| 8 | 311168 |
| 9 | 2149888 |
| 10 | 15049216 |
| 11 | 106502144 |
| 12 | 760729600 |
| 13 | 5477253120 |
| 14 | 39710085120 |
| 15 | 289650032640 |
| 16 | 2124100239360 |
| 17 | 15651264921600 |
| 18 | 115819360419840 |
| 19 | 860372391690240 |
[1,5,28,168,1056,6864,45760,311168,2149888, 15049216,106502144,760729600,5477253120, 39710085120,289650032640,2124100239360, 15651264921600,115819360419840,860372391690240] |