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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 120 |
| 5 | 1320 |
| 6 | 15480 |
| 7 | 199080 |
| 8 | 2862720 |
| 9 | 46146240 |
| 10 | 826156800 |
| 11 | 16212873600 |
| 12 | 344741443200 |
| 13 | 7875365097600 |
| 14 | 192137321376000 |
| 15 | 4984375210214400 |
| 16 | 136994756496998400 |
| 17 | 3976455027389644800 |
| 18 | 121533921410994892800 |
| 19 | 3900447928934548992000 |
[1,1,2,12,120,1320,15480,199080,2862720,46146240, 826156800,16212873600,344741443200,7875365097600, 192137321376000,4984375210214400, 136994756496998400,3976455027389644800, 121533921410994892800,3900447928934548992000] |