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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 1 |
| 2 | 64 |
| 3 | 900 |
| 4 | 5184 |
| 5 | 32400 |
| 6 | 57600 |
| 7 | 176400 |
| 8 | 705600 |
| 9 | 1166400 |
| 10 | 3240000 |
| 11 | 6350400 |
| 12 | 14288400 |
| 13 | 37454400 |
| 14 | 25401600 |
| 15 | 87609600 |
[2,1,64,900,5184,32400,57600,176400,705600, 1166400,3240000,6350400,14288400,37454400, 25401600,87609600] |