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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 840 |
| 2 | 2771340 |
| 3 | 10754814720 |
| 4 | 44524428808860 |
| 5 | 190847602744995840 |
| 6 | 835982760936614190900 |
| 7 | 3716634993696885851422720 |
| 8 | 16702642470437308383606668060 |
| 9 | 75679458912906782280286032887808 |
| 10 | 345116202503279265243707597937393840 |
| 11 | 1581997780375359530321517073184807976960 |
[1,840,2771340,10754814720,44524428808860, 190847602744995840,835982760936614190900, 3716634993696885851422720, 16702642470437308383606668060, 75679458912906782280286032887808, 345116202503279265243707597937393840, 1581997780375359530321517073184807976960] |