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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 12 |
| 3 | 135 |
| 4 | 1680 |
| 5 | 23625 |
| 6 | 374220 |
| 7 | 6621615 |
| 8 | 129729600 |
| 9 | 2791213425 |
| 10 | 65472907500 |
| 11 | 1663666579575 |
| 12 | 45537716624400 |
| 13 | 1336089255125625 |
| 14 | 41837777148667500 |
| 15 | 1392813754566609375 |
| 16 | 49126088694402720000 |
| 17 | 1830138702650463830625 |
| 18 | 71812362934450726087500 |
[0,1,12,135,1680,23625,374220,6621615,129729600, 2791213425,65472907500,1663666579575, 45537716624400,1336089255125625,41837777148667500, 1392813754566609375,49126088694402720000, 1830138702650463830625,71812362934450726087500] |