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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 8 |
| 5 | 405 |
| 6 | 2520 |
| 7 | 4320 |
| 8 | 32781000 |
| 9 | 256556160 |
| 10 | 10590199200 |
| 11 | 2225341641600 |
| 12 | 28746722188800 |
[1,1,1,8,405,2520,4320,32781000,256556160, 10590199200,2225341641600,28746722188800] |