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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 13 |
| 4 | 28 |
| 5 | 270 |
| 6 | 1176 |
| 7 | 7952 |
| 8 | 43772 |
| 9 | 285525 |
| 10 | 1808560 |
| 11 | 12186394 |
| 12 | 82828916 |
| 13 | 578556693 |
| 14 | 4088706356 |
| 15 | 29246505510 |
| 16 | 210592755064 |
[1,13,28,270,1176,7952,43772,285525,1808560, 12186394,82828916,578556693,4088706356, 29246505510,210592755064] |