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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 15 |
| 5 | 90 |
| 6 | 10 |
| 7 | 3 |
| 8 | 9003 |
| 9 | 45300 |
| 10 | 9570 |
| 11 | 5840220 |
| 12 | 533564010 |
| 13 | 5384225220 |
| 14 | 412190739351 |
| 15 | 244816773411 |
| 16 | 682660400311 |
| 17 | 275258914747246 |
| 18 | 710284752537711 |
| 19 | 152042178127701610 |
| 20 | 6144469158651504786 |
| 21 | 8516189439015621936 |
[0,1,6,15,90,10,3,9003,45300,9570,5840220, 533564010,5384225220,412190739351,244816773411, 682660400311,275258914747246,710284752537711, 152042178127701610,6144469158651504786, 8516189439015621936] |