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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 36 |
| 4 | 180 |
| 5 | 1260 |
| 6 | 12600 |
| 7 | 189000 |
| 8 | 4347000 |
| 9 | 156492000 |
| 10 | 8920044000 |
| 11 | 811724004000 |
| 12 | 118511704584000 |
| 13 | 27850250577240000 |
| 14 | 10555244968773960000 |
| 15 | 6459809920889663520000 |
| 16 | 6388752011759877221280000 |
| 17 | 10215614466804043676826720000 |
| 18 | 26417579011155256948273897920000 |
[1,3,9,36,180,1260,12600,189000,4347000,156492000, 8920044000,811724004000,118511704584000, 27850250577240000,10555244968773960000, 6459809920889663520000,6388752011759877221280000, 10215614466804043676826720000, 26417579011155256948273897920000] |