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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 20 |
| 4 | 464 |
| 5 | 22564 |
| 6 | 2472584 |
| 7 | 603871080 |
| 8 | 327862785884 |
| 9 | 395850912855384 |
| 10 | 1063574508841830552 |
| 11 | 6358546221961060404292 |
| 12 | 84578736940287879637237736 |
[1,2,20,464,22564,2472584,603871080,327862785884, 395850912855384,1063574508841830552, 6358546221961060404292,84578736940287879637237736] |