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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 51 |
| 5 | 187 |
| 6 | 828 |
| 7 | 3392 |
| 8 | 15582 |
| 9 | 67025 |
| 10 | 312769 |
| 11 | 1393236 |
| 12 | 6588826 |
| 13 | 29978985 |
| 14 | 143025403 |
| 15 | 661778961 |
| 16 | 3177477385 |
| 17 | 14873762054 |
| 18 | 71793720043 |
| 19 | 339223544275 |
| 20 | 1643657134717 |
| 21 | 7822576163185 |
| 22 | 38030427258027 |
| 23 | 182051826849128 |
| 24 | 887368504414777 |
| 25 | 4268323532093230 |
| 26 | 20851877813312252 |
| 27 | 100694489250187695 |
[1,1,4,12,51,187,828,3392,15582,67025,312769, 1393236,6588826,29978985,143025403,661778961, 3177477385,14873762054,71793720043,339223544275, 1643657134717,7822576163185,38030427258027, 182051826849128,887368504414777,4268323532093230, 20851877813312252,100694489250187695] |