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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 21 |
| 4 | 234 |
| 5 | 3590 |
| 6 | 70254 |
| 7 | 1672972 |
| 8 | 46955760 |
| 9 | 1517994792 |
| 10 | 55549351800 |
| 11 | 2269918543640 |
| 12 | 102452561694864 |
| 13 | 5062050729973120 |
| 14 | 271751784988056576 |
| 15 | 15750949414628405760 |
| 16 | 980315266648197537792 |
| 17 | 65207656047198387921536 |
[1,3,21,234,3590,70254,1672972,46955760, 1517994792,55549351800,2269918543640, 102452561694864,5062050729973120, 271751784988056576,15750949414628405760, 980315266648197537792,65207656047198387921536] |