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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 25 |
| 5 | 66 |
| 6 | 177 |
| 7 | 484 |
| 8 | 1339 |
| 9 | 3742 |
| 10 | 10538 |
| 11 | 29866 |
| 12 | 85087 |
| 13 | 243478 |
| 14 | 699324 |
| 15 | 2015082 |
| 16 | 5822619 |
| 17 | 16865718 |
| 18 | 48958404 |
| 19 | 142390542 |
| 20 | 414837699 |
| 21 | 1210439958 |
| 22 | 3536809521 |
| 23 | 10347314544 |
| 24 | 30306977757 |
| 25 | 88861597426 |
| 26 | 260798283502 |
| 27 | 766092871654 |
| 28 | 2252240916665 |
[1,2,4,10,25,66,177,484,1339,3742,10538,29866, 85087,243478,699324,2015082,5822619,16865718, 48958404,142390542,414837699,1210439958, 3536809521,10347314544,30306977757,88861597426, 260798283502,766092871654,2252240916665] |