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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 72 |
| 4 | 361 |
| 5 | 1840 |
| 6 | 9505 |
| 7 | 49578 |
| 8 | 260540 |
| 9 | 1377328 |
| 10 | 7316373 |
| 11 | 39020372 |
| 12 | 208809544 |
| 13 | 1120621368 |
| 14 | 6029023185 |
| 15 | 32507001876 |
| 16 | 175604614108 |
| 17 | 950233307930 |
| 18 | 5149691511432 |
| 19 | 27946158749572 |
| 20 | 151843410356906 |
| 21 | 825949622559366 |
[1,3,15,72,361,1840,9505,49578,260540,1377328, 7316373,39020372,208809544,1120621368,6029023185, 32507001876,175604614108,950233307930, 5149691511432,27946158749572,151843410356906, 825949622559366] |