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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 13 |
| 2 | 117 |
| 3 | 905 |
| 4 | 6461 |
| 5 | 43953 |
| 6 | 289717 |
| 7 | 1868425 |
| 8 | 11861421 |
| 9 | 74423393 |
| 10 | 462815717 |
| 11 | 2858273145 |
| 12 | 17556537181 |
| 13 | 107373722833 |
| 14 | 654414852117 |
| 15 | 3977351721065 |
| 16 | 24118423433741 |
| 17 | 145982106270273 |
| 18 | 882250466222917 |
[1,13,117,905,6461,43953,289717,1868425,11861421, 74423393,462815717,2858273145,17556537181, 107373722833,654414852117,3977351721065, 24118423433741,145982106270273,882250466222917] |