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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 26 |
| 4 | 103 |
| 5 | 426 |
| 6 | 1817 |
| 7 | 7905 |
| 8 | 34999 |
| 9 | 156978 |
| 10 | 711572 |
| 11 | 3254200 |
| 12 | 14992984 |
| 13 | 69508490 |
| 14 | 324005487 |
| 15 | 1517421717 |
| 16 | 7135832181 |
| 17 | 33679784580 |
| 18 | 159477986279 |
| 19 | 757336398740 |
| 20 | 3605893799280 |
| 21 | 17209257753242 |
| 22 | 82307977414514 |
| 23 | 394432975779016 |
| 24 | 1893578180925439 |
| 25 | 9105600973099922 |
| 26 | 43852562469867462 |
| 27 | 211491091134032890 |
[1,2,7,26,103,426,1817,7905,34999,156978,711572, 3254200,14992984,69508490,324005487,1517421717, 7135832181,33679784580,159477986279,757336398740, 3605893799280,17209257753242,82307977414514, 394432975779016,1893578180925439,9105600973099922, 43852562469867462,211491091134032890] |