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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 32 |
| 5 | 396 |
| 6 | 6692 |
| 7 | 143816 |
| 8 | 3756104 |
| 9 | 115553024 |
| 10 | 4093236352 |
| 11 | 164098040448 |
| 12 | 7345463787136 |
| 13 | 363154251536896 |
| 14 | 19653476190481408 |
| 15 | 1155636468524067328 |
| 16 | 73364615077878838784 |
| 17 | 5001199614295920565248 |
| 18 | 364363128390631094137856 |
[1,1,1,4,32,396,6692,143816,3756104,115553024, 4093236352,164098040448,7345463787136, 363154251536896,19653476190481408, 1155636468524067328,73364615077878838784, 5001199614295920565248,364363128390631094137856] |