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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 13 |
| 4 | 55 |
| 5 | 276 |
| 6 | 1656 |
| 7 | 11596 |
| 8 | 92775 |
| 9 | 834978 |
| 10 | 8349781 |
| 11 | 91847594 |
| 12 | 1102171133 |
| 13 | 14328224732 |
| 14 | 200595146260 |
| 15 | 3008927193906 |
| 16 | 48142835102504 |
| 17 | 818428196742571 |
| 18 | 14731707541366281 |
| 19 | 279902443285959353 |
| 20 | 5598048865719187061 |
[2,4,13,55,276,1656,11596,92775,834978,8349781, 91847594,1102171133,14328224732,200595146260, 3008927193906,48142835102504,818428196742571, 14731707541366281,279902443285959353, 5598048865719187061] |