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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 16 |
| 3 | 116 |
| 4 | 1456 |
| 5 | 18272 |
| 6 | 315424 |
| 7 | 5592512 |
| 8 | 123304192 |
| 9 | 2814746624 |
| 10 | 75639399424 |
| 11 | 2108241486848 |
| 12 | 66872341633024 |
| 13 | 2198914617257984 |
| 14 | 80437062279012352 |
| 15 | 3046047243283570688 |
| 16 | 126259635313097506816 |
| 17 | 5408763597941368291328 |
| 18 | 250569314672586154835968 |
[1,2,16,116,1456,18272,315424,5592512,123304192, 2814746624,75639399424,2108241486848, 66872341633024,2198914617257984,80437062279012352, 3046047243283570688,126259635313097506816, 5408763597941368291328,250569314672586154835968] |