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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 120 |
| 4 | 2520 |
| 5 | 51840 |
| 6 | 2494800 |
| 7 | 6227020800 |
| 8 | 653837184000 |
| 9 | 27360571392000 |
| 10 | 30411275102208000 |
| 11 | 51090942171709440000 |
| 12 | 1846572624206069760000 |
| 13 | 15511210043330985984000000 |
| 14 | 1361108681302294020096000000 |
| 15 | 8841761993739701954543616000000 |
[1,3,120,2520,51840,2494800,6227020800, 653837184000,27360571392000,30411275102208000, 51090942171709440000,1846572624206069760000, 15511210043330985984000000, 1361108681302294020096000000, 8841761993739701954543616000000] |