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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 80 |
| 3 | 4480 |
| 4 | 389376 |
| 5 | 46137344 |
| 6 | 6939332608 |
| 7 | 1266556600320 |
| 8 | 272000000000000 |
| 9 | 67204714785144832 |
| 10 | 18780742521990414336 |
| 11 | 5857307089452073484288 |
| 12 | 2016866466756967373209600 |
| 13 | 759982437118771200000000000 |
| 14 | 311070869724989874190180941824 |
| 15 | 137440072511222468264810285891584 |
[1,3,80,4480,389376,46137344,6939332608, 1266556600320,272000000000000,67204714785144832, 18780742521990414336,5857307089452073484288, 2016866466756967373209600, 759982437118771200000000000, 311070869724989874190180941824, 137440072511222468264810285891584] |