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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 28 |
| 4 | 275 |
| 5 | 3126 |
| 6 | 37632 |
| 7 | 475056 |
| 8 | 6192531 |
| 9 | 82754650 |
| 10 | 1127504378 |
| 11 | 15603575208 |
| 12 | 218727171104 |
| 13 | 3099183987004 |
| 14 | 44315462038200 |
| 15 | 638663235342528 |
| 16 | 9267264584278419 |
| 17 | 135279095477748642 |
| 18 | 1985221072388231742 |
[1,3,28,275,3126,37632,475056,6192531,82754650, 1127504378,15603575208,218727171104,3099183987004, 44315462038200,638663235342528,9267264584278419, 135279095477748642,1985221072388231742] |