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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 4 |
| 4 | 32 |
| 5 | 180 |
| 6 | 1152 |
| 7 | 6636 |
| 8 | 40384 |
| 9 | 266964 |
| 10 | 1800360 |
| 11 | 12127016 |
| 12 | 82960512 |
| 13 | 576835428 |
| 14 | 4054304072 |
| 15 | 28728093520 |
| 16 | 205123982848 |
[2,4,32,180,1152,6636,40384,266964,1800360, 12127016,82960512,576835428,4054304072, 28728093520,205123982848] |