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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 20 |
| 4 | 35 |
| 5 | 126 |
| 6 | 210 |
| 7 | 792 |
| 8 | 1287 |
| 9 | 5005 |
| 10 | 8008 |
| 11 | 31824 |
| 12 | 50388 |
| 13 | 203490 |
| 14 | 319770 |
| 15 | 1307504 |
| 16 | 2042975 |
| 17 | 8436285 |
| 18 | 13123110 |
| 19 | 54627300 |
| 20 | 84672315 |
| 21 | 354817320 |
| 22 | 548354040 |
| 23 | 2310789600 |
| 24 | 3562467300 |
| 25 | 15084504396 |
| 26 | 23206929840 |
| 27 | 98672427616 |
| 28 | 151532656696 |
[1,3,6,20,35,126,210,792,1287,5005,8008,31824, 50388,203490,319770,1307504,2042975,8436285, 13123110,54627300,84672315,354817320,548354040, 2310789600,3562467300,15084504396,23206929840, 98672427616,151532656696] |