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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 60 |
| 6 | 210 |
| 7 | 754 |
| 8 | 2766 |
| 9 | 10280 |
| 10 | 38568 |
| 11 | 145770 |
| 12 | 554162 |
| 13 | 2116568 |
| 14 | 8115660 |
| 15 | 31220672 |
| 16 | 120442860 |
| 17 | 465775226 |
| 18 | 1805074882 |
| 19 | 7008550224 |
| 20 | 27257398714 |
| 21 | 106166467074 |
| 22 | 414068416752 |
| 23 | 1616899329454 |
| 24 | 6320798698322 |
| 25 | 24734167234028 |
| 26 | 96877398455260 |
| 27 | 379765373701964 |
| 28 | 1489867265555382 |
| 29 | 5849164981941642 |
| 30 | 22979031257945948 |
[1,1,2,6,18,60,210,754,2766,10280,38568,145770, 554162,2116568,8115660,31220672,120442860, 465775226,1805074882,7008550224,27257398714, 106166467074,414068416752,1616899329454, 6320798698322,24734167234028,96877398455260, 379765373701964,1489867265555382,5849164981941642, 22979031257945948] |