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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 105 |
| 5 | 252 |
| 6 | 2310 |
| 7 | 25740 |
| 8 | 9009 |
| 9 | 136136 |
| 10 | 11639628 |
| 11 | 10581480 |
| 12 | 223092870 |
| 13 | 1029659400 |
| 14 | 2868336900 |
| 15 | 11090902680 |
| 16 | 644658718275 |
| 17 | 606737617200 |
| 18 | 4011209802600 |
| 19 | 140603459396400 |
| 20 | 133573286426580 |
| 21 | 5215718803323600 |
[1,3,10,105,252,2310,25740,9009,136136,11639628, 10581480,223092870,1029659400,2868336900, 11090902680,644658718275,606737617200, 4011209802600,140603459396400,133573286426580, 5215718803323600] |