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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 70 |
| 5 | 257 |
| 6 | 967 |
| 7 | 3722 |
| 8 | 14548 |
| 9 | 57619 |
| 10 | 230612 |
| 11 | 931083 |
| 12 | 3787276 |
| 13 | 15502881 |
| 14 | 63810147 |
| 15 | 263909613 |
| 16 | 1096140669 |
| 17 | 4570019368 |
| 18 | 19117859437 |
| 19 | 80220313298 |
| 20 | 337542496835 |
| 21 | 1423849191982 |
| 22 | 6020011578673 |
| 23 | 25506250066482 |
| 24 | 108277897776181 |
| 25 | 460482597553895 |
| 26 | 1961598838029100 |
| 27 | 8369127049893122 |
[1,2,6,20,70,257,967,3722,14548,57619,230612, 931083,3787276,15502881,63810147,263909613, 1096140669,4570019368,19117859437,80220313298, 337542496835,1423849191982,6020011578673, 25506250066482,108277897776181,460482597553895, 1961598838029100,8369127049893122] |