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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 14 |
| 4 | 82 |
| 5 | 610 |
| 6 | 5450 |
| 7 | 56700 |
| 8 | 674520 |
| 9 | 9027480 |
| 10 | 134236200 |
| 11 | 2195701200 |
| 12 | 39180094800 |
| 13 | 757389032400 |
| 14 | 15767305554000 |
| 15 | 351689317980000 |
| 16 | 8367381470448000 |
| 17 | 211518767796336000 |
| 18 | 5661504152255952000 |
| 19 | 159954273475764768000 |
| 20 | 4757034049019572320000 |
| 21 | 148547713504322452320000 |
| 22 | 4859583724723970642400000 |
[1,1,3,14,82,610,5450,56700,674520,9027480, 134236200,2195701200,39180094800,757389032400, 15767305554000,351689317980000,8367381470448000, 211518767796336000,5661504152255952000, 159954273475764768000,4757034049019572320000, 148547713504322452320000, 4859583724723970642400000] |