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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 44 |
| 5 | 300 |
| 6 | 2420 |
| 7 | 22460 |
| 8 | 235260 |
| 9 | 2741660 |
| 10 | 35152820 |
| 11 | 491459820 |
| 12 | 7436765660 |
| 13 | 121046445260 |
| 14 | 2108118579060 |
| 15 | 39104985755420 |
| 16 | 769549656815420 |
| 17 | 16009942093608060 |
| 18 | 351030466622487860 |
| 19 | 8089084984387984460 |
| 20 | 195421894806240545820 |
| 21 | 4938445392988428283820 |
[1,2,8,44,300,2420,22460,235260,2741660,35152820, 491459820,7436765660,121046445260,2108118579060, 39104985755420,769549656815420,16009942093608060, 351030466622487860,8089084984387984460, 195421894806240545820,4938445392988428283820] |