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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 56 |
| 3 | 368 |
| 4 | 2336 |
| 5 | 14528 |
| 6 | 89216 |
| 7 | 543488 |
| 8 | 3293696 |
| 9 | 19893248 |
| 10 | 119883776 |
| 11 | 721399808 |
| 12 | 4336787456 |
| 13 | 26054279168 |
| 14 | 156459892736 |
| 15 | 939296227328 |
| 16 | 5637924847616 |
| 17 | 33836139020288 |
| 18 | 203051193860096 |
| 19 | 1218444602114048 |
[1,8,56,368,2336,14528,89216,543488,3293696, 19893248,119883776,721399808,4336787456, 26054279168,156459892736,939296227328, 5637924847616,33836139020288,203051193860096, 1218444602114048] |