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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 1080 |
| 3 | 408240 |
| 4 | 29393280 |
| 5 | 215550720 |
| 6 | 648499737600 |
| 7 | 953294614272000 |
| 8 | 2333665215737856000 |
| 9 | 7183021534041120768000 |
| 10 | 232066849561328517120000 |
| 11 | 723095875143672151080960000 |
| 12 | 74189636789740762700906496000000 |
[1,18,1080,408240,29393280,215550720,648499737600, 953294614272000,2333665215737856000, 7183021534041120768000,232066849561328517120000, 723095875143672151080960000, 74189636789740762700906496000000] |