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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 16 |
| 4 | 133 |
| 5 | 1561 |
| 6 | 24374 |
| 7 | 485640 |
| 8 | 11969843 |
| 9 | 356348290 |
| 10 | 12572687675 |
| 11 | 517644938724 |
| 12 | 24553141710156 |
| 13 | 1327223189312606 |
| 14 | 81005220402829714 |
| 15 | 5537660009982114858 |
| 16 | 421050946315817655785 |
| 17 | 35387457515051683169307 |
| 18 | 3269500807582223015227780 |
[1,1,3,16,133,1561,24374,485640,11969843, 356348290,12572687675,517644938724,24553141710156, 1327223189312606,81005220402829714, 5537660009982114858,421050946315817655785, 35387457515051683169307,3269500807582223015227780] |