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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 72 |
| 4 | 6690 |
| 5 | 1536000 |
| 6 | 1398496680 |
| 7 | 4165565871600 |
| 8 | 48724656010825410 |
| 9 | 1991141239554487077120 |
| 10 | 325362786100184356140612996 |
| 11 | 190695111051826003327799496771600 |
| 12 | 452459020719698368348441955010421696800 |
[1,0,6,72,6690,1536000,1398496680,4165565871600, 48724656010825410,1991141239554487077120, 325362786100184356140612996, 190695111051826003327799496771600, 452459020719698368348441955010421696800] |