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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 56 |
| 3 | 384 |
| 4 | 2648 |
| 5 | 18496 |
| 6 | 131008 |
| 7 | 940032 |
| 8 | 6821848 |
| 9 | 49985984 |
| 10 | 369258560 |
| 11 | 2746629120 |
| 12 | 20549693888 |
| 13 | 154518118912 |
| 14 | 1166873394688 |
| 15 | 8844937101312 |
| 16 | 67265481552856 |
| 17 | 513038965707968 |
| 18 | 3923108472072512 |
| 19 | 30068733313938432 |
| 20 | 230943237733355840 |
| 21 | 1777114026405752320 |
[1,8,56,384,2648,18496,131008,940032,6821848, 49985984,369258560,2746629120,20549693888, 154518118912,1166873394688,8844937101312, 67265481552856,513038965707968,3923108472072512, 30068733313938432,230943237733355840, 1777114026405752320] |