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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 33 |
| 4 | 436 |
| 5 | 8122 |
| 6 | 197920 |
| 7 | 6007205 |
| 8 | 219413116 |
| 9 | 9402081718 |
| 10 | 463548752912 |
| 11 | 25893783163498 |
| 12 | 1618536618626888 |
| 13 | 112053082721454708 |
| 14 | 8518619080226661504 |
| 15 | 705977323976245345133 |
| 16 | 63382036275445226941548 |
[1,1,4,33,436,8122,197920,6007205,219413116, 9402081718,463548752912,25893783163498, 1618536618626888,112053082721454708, 8518619080226661504,705977323976245345133, 63382036275445226941548] |