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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 24 |
| 5 | 129 |
| 6 | 600 |
| 7 | 4815 |
| 8 | 40320 |
| 9 | 313425 |
| 10 | 3900960 |
| 11 | 39023775 |
| 12 | 399168000 |
| 13 | 6335076825 |
| 14 | 83286403200 |
| 15 | 1169542749375 |
| 16 | 20922789888000 |
| 17 | 359796258446625 |
| 18 | 5529827983680000 |
| 19 | 120457648437501375 |
| 20 | 2615369658789888000 |
| 21 | 40723609672075955625 |
[1,2,5,24,129,600,4815,40320,313425,3900960, 39023775,399168000,6335076825,83286403200, 1169542749375,20922789888000,359796258446625, 5529827983680000,120457648437501375, 2615369658789888000,40723609672075955625] |