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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 25 |
| 4 | 88 |
| 5 | 311 |
| 6 | 1114 |
| 7 | 4050 |
| 8 | 14917 |
| 9 | 55528 |
| 10 | 208459 |
| 11 | 787920 |
| 12 | 2994655 |
| 13 | 11433998 |
| 14 | 43824437 |
| 15 | 168520201 |
| 16 | 649840740 |
| 17 | 2512011359 |
| 18 | 9731179138 |
| 19 | 37768570827 |
| 20 | 146833956266 |
| 21 | 571711568905 |
| 22 | 2229035221824 |
| 23 | 8701426599353 |
| 24 | 34005503702176 |
| 25 | 133030452858279 |
| 26 | 520905732440782 |
[1,2,7,25,88,311,1114,4050,14917,55528,208459, 787920,2994655,11433998,43824437,168520201, 649840740,2512011359,9731179138,37768570827, 146833956266,571711568905,2229035221824, 8701426599353,34005503702176,133030452858279, 520905732440782] |