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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 20 |
| 5 | 804 |
| 6 | 108304 |
| 7 | 49833296 |
| 8 | 87606851264 |
| 9 | 641794234287360 |
| 10 | 19783636266156204928 |
| 11 | 2512584289692759254055168 |
| 12 | 1295158553795409705964052724736 |
| 13 | 2690610592205668589191756477437574144 |
[1,1,2,20,804,108304,49833296,87606851264, 641794234287360,19783636266156204928, 2512584289692759254055168, 1295158553795409705964052724736, 2690610592205668589191756477437574144] |