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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 | 2259801992 |
| 12 | 15818613944 |
| 13 | 110730297580 |
| 14 | 775112082864 |
| 15 | 5425784578704 |
| 16 | 37980492041520 |
| 17 | 265863444224784 |
| 18 | 1861044109112496 |
| 19 | 13027308760560528 |
[1,8,56,392,2744,19208,134456,941192,6588344, 46118408,322828856,2259801992,15818613944, 110730297580,775112082864,5425784578704, 37980492041520,265863444224784,1861044109112496, 13027308760560528] |