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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 10 |
| 3 | 20 |
| 4 | 70 |
| 5 | 126 |
| 6 | 462 |
| 7 | 792 |
| 8 | 3003 |
| 9 | 5005 |
| 10 | 19448 |
| 11 | 31824 |
| 12 | 125970 |
| 13 | 203490 |
| 14 | 817190 |
| 15 | 1307504 |
| 16 | 5311735 |
| 17 | 8436285 |
| 18 | 34597290 |
| 19 | 54627300 |
| 20 | 225792840 |
| 21 | 354817320 |
| 22 | 1476337800 |
| 23 | 2310789600 |
| 24 | 9669554100 |
| 25 | 15084504396 |
| 26 | 63432274896 |
| 27 | 98672427616 |
[1,3,10,20,70,126,462,792,3003,5005,19448,31824, 125970,203490,817190,1307504,5311735,8436285, 34597290,54627300,225792840,354817320,1476337800, 2310789600,9669554100,15084504396,63432274896, 98672427616] |