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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 76 |
| 5 | 299 |
| 6 | 1236 |
| 7 | 5232 |
| 8 | 22675 |
| 9 | 99949 |
| 10 | 447039 |
| 11 | 2022251 |
| 12 | 9240139 |
| 13 | 42562644 |
| 14 | 197455398 |
| 15 | 921601823 |
| 16 | 4324286790 |
| 17 | 20384608216 |
| 18 | 96487680824 |
| 19 | 458373282220 |
| 20 | 2184643468897 |
| 21 | 10442572405289 |
| 22 | 50046778230613 |
| 23 | 240424223189811 |
| 24 | 1157493695441397 |
| 25 | 5583603936153083 |
| 26 | 26983173704954285 |
| 27 | 130613769257910958 |
[1,2,6,20,76,299,1236,5232,22675,99949,447039, 2022251,9240139,42562644,197455398,921601823, 4324286790,20384608216,96487680824,458373282220, 2184643468897,10442572405289,50046778230613, 240424223189811,1157493695441397,5583603936153083, 26983173704954285,130613769257910958] |