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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 8 |
| 3 | 40 |
| 4 | 257 |
| 5 | 1534 |
| 6 | 9314 |
| 7 | 56314 |
| 8 | 341988 |
| 9 | 2082546 |
| 10 | 12729304 |
| 11 | 78083158 |
| 12 | 480688451 |
| 13 | 2969319278 |
| 14 | 18402445258 |
| 15 | 114405090020 |
| 16 | 713334999381 |
| 17 | 4460132045862 |
| 18 | 27960102769656 |
| 19 | 175711836643538 |
| 20 | 1106809365488500 |
| 21 | 6987092970919342 |
[0,8,40,257,1534,9314,56314,341988,2082546, 12729304,78083158,480688451,2969319278, 18402445258,114405090020,713334999381, 4460132045862,27960102769656,175711836643538, 1106809365488500,6987092970919342] |