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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 40 |
| 4 | 224 |
| 5 | 1328 |
| 6 | 8128 |
| 7 | 51664 |
| 8 | 344864 |
| 9 | 2419808 |
| 10 | 17690624 |
| 11 | 133255936 |
| 12 | 1025049088 |
| 13 | 8010533504 |
| 14 | 63486137600 |
| 15 | 510583994560 |
| 16 | 4173502486400 |
| 17 | 34713858911872 |
| 18 | 293845548560384 |
| 19 | 2528481737709056 |
| 20 | 22072195485742080 |
| 21 | 194999285532239872 |
| 22 | 1739475973516343296 |
[1,2,8,40,224,1328,8128,51664,344864,2419808, 17690624,133255936,1025049088,8010533504, 63486137600,510583994560,4173502486400, 34713858911872,293845548560384,2528481737709056, 22072195485742080,194999285532239872, 1739475973516343296] |