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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 56 |
| 3 | 392 |
| 4 | 2744 |
| 5 | 19208 |
| 6 | 134456 |
| 7 | 941192 |
| 8 | 6588344 |
| 9 | 46118408 |
| 10 | 322828856 |
| 11 | 2259801964 |
| 12 | 15818613552 |
| 13 | 110730293520 |
| 14 | 775112045232 |
| 15 | 5425784250768 |
| 16 | 37980489294384 |
| 17 | 265863421833744 |
| 18 | 1861043930247600 |
| 19 | 13027307353612944 |
[1,8,56,392,2744,19208,134456,941192,6588344, 46118408,322828856,2259801964,15818613552, 110730293520,775112045232,5425784250768, 37980489294384,265863421833744,1861043930247600, 13027307353612944] |