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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 132 |
| 5 | 2040 |
| 6 | 40440 |
| 7 | 979440 |
| 8 | 28034160 |
| 9 | 925858080 |
| 10 | 34654465440 |
| 11 | 1449705660480 |
| 12 | 67029745527360 |
| 13 | 3394417068282240 |
| 14 | 186842736763562880 |
| 15 | 11107390768144070400 |
| 16 | 709223357051739129600 |
| 17 | 48408150749346010022400 |
| 18 | 3517279496138031162739200 |
| 19 | 271050342684747077612160000 |
[1,2,12,132,2040,40440,979440,28034160,925858080, 34654465440,1449705660480,67029745527360, 3394417068282240,186842736763562880, 11107390768144070400,709223357051739129600, 48408150749346010022400,3517279496138031162739200, 271050342684747077612160000] |