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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 9 |
| 3 | 720 |
| 4 | 56880 |
| 5 | 4492809 |
| 6 | 354875040 |
| 7 | 28030635360 |
| 8 | 2214065318409 |
| 9 | 174883129518960 |
| 10 | 13813553166679440 |
| 11 | 1091095817038156809 |
| 12 | 86182755992847708480 |
| 13 | 6807346627617930813120 |
| 14 | 537694200825823686528009 |
| 15 | 42471034518612453304899600 |
| 16 | 3354674032769557987400540400 |
[0,9,720,56880,4492809,354875040,28030635360, 2214065318409,174883129518960,13813553166679440, 1091095817038156809,86182755992847708480, 6807346627617930813120,537694200825823686528009, 42471034518612453304899600, 3354674032769557987400540400] |