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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 46 |
| 5 | 420 |
| 6 | 5185 |
| 7 | 77658 |
| 8 | 1376768 |
| 9 | 28133616 |
| 10 | 651325653 |
| 11 | 16846515510 |
| 12 | 481472773386 |
| 13 | 15067838554860 |
| 14 | 512473605894549 |
| 15 | 18821719654854998 |
| 16 | 742395982483047976 |
| 17 | 31299550394528466960 |
| 18 | 1404629090183809673484 |
| 19 | 66851805805525048040334 |
| 20 | 3363381327122907537090234 |
[1,2,6,46,420,5185,77658,1376768,28133616, 651325653,16846515510,481472773386,15067838554860, 512473605894549,18821719654854998, 742395982483047976,31299550394528466960, 1404629090183809673484,66851805805525048040334, 3363381327122907537090234] |