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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 66 |
| 5 | 212 |
| 6 | 666 |
| 7 | 2060 |
| 8 | 6306 |
| 9 | 19172 |
| 10 | 58026 |
| 11 | 175100 |
| 12 | 527346 |
| 13 | 1586132 |
| 14 | 4766586 |
| 15 | 14316140 |
| 16 | 42981186 |
| 17 | 129009092 |
| 18 | 387158346 |
| 19 | 1161737180 |
| 20 | 3485735826 |
| 21 | 10458256052 |
| 22 | 31376865306 |
| 23 | 94134790220 |
| 24 | 282412759266 |
| 25 | 847255055012 |
[1,2,6,20,66,212,666,2060,6306,19172,58026,175100, 527346,1586132,4766586,14316140,42981186, 129009092,387158346,1161737180,3485735826, 10458256052,31376865306,94134790220,282412759266, 847255055012] |