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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 45 |
| 6 | 150 |
| 7 | 500 |
| 8 | 1768 |
| 9 | 6449 |
| 10 | 23952 |
| 11 | 90754 |
| 12 | 350352 |
| 13 | 1366671 |
| 14 | 5412378 |
| 15 | 21657356 |
| 16 | 87478719 |
| 17 | 356678716 |
| 18 | 1465294690 |
| 19 | 6061674645 |
| 20 | 25247400391 |
| 21 | 105746887056 |
| 22 | 445393747063 |
| 23 | 1885309697875 |
| 24 | 8016785181291 |
| 25 | 34236548716423 |
| 26 | 146792552622838 |
| 27 | 631691350559110 |
| 28 | 2727914538208874 |
[1,1,2,5,15,45,150,500,1768,6449,23952,90754, 350352,1366671,5412378,21657356,87478719, 356678716,1465294690,6061674645,25247400391, 105746887056,445393747063,1885309697875, 8016785181291,34236548716423,146792552622838, 631691350559110,2727914538208874] |