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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 67 |
| 3 | 1024 |
| 4 | 19710 |
| 5 | 456720 |
| 6 | 12372360 |
| 7 | 383685120 |
| 8 | 13406178240 |
| 9 | 521194867200 |
| 10 | 22318001798400 |
| 11 | 1043827513344000 |
| 12 | 52949040240096000 |
| 13 | 2895555891900672000 |
| 14 | 169823181579891840000 |
| 15 | 10633812541718446080000 |
| 16 | 708077586604965857280000 |
| 17 | 49962245750984840232960000 |
[1,6,67,1024,19710,456720,12372360,383685120, 13406178240,521194867200,22318001798400, 1043827513344000,52949040240096000, 2895555891900672000,169823181579891840000, 10633812541718446080000,708077586604965857280000, 49962245750984840232960000] |