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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 1 |
| 6 | 2 |
| 7 | 8 |
| 8 | 42 |
| 9 | 296 |
| 10 | 2635 |
| 11 | 25626 |
| 12 | 268394 |
| 13 | 2937495 |
| 14 | 33310550 |
| 15 | 388431688 |
| 16 | 4637550072 |
| 17 | 56493493990 |
| 18 | 700335433295 |
[1,1,2,8,42,296,2635,25626,268394,2937495, 33310550,388431688,4637550072,56493493990, 700335433295] |