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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 35 |
| 4 | 20 |
| 5 | 3003 |
| 6 | 560 |
| 7 | 692835 |
| 8 | 4620 |
| 9 | 185910725 |
| 10 | 48048 |
| 11 | 136745788725 |
| 12 | 1361360 |
| 13 | 4281195077775 |
| 14 | 22170720 |
| 15 | 6541380665835015 |
| 16 | 446185740 |
| 17 | 1898924328582105825 |
| 18 | 5949143200 |
| 19 | 90048990529077755175 |
[1,4,35,20,3003,560,692835,4620,185910725,48048, 136745788725,1361360,4281195077775,22170720, 6541380665835015,446185740,1898924328582105825, 5949143200,90048990529077755175] |