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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 27 |
| 5 | 285 |
| 6 | 3585 |
| 7 | 56595 |
| 8 | 1062131 |
| 9 | 22868685 |
| 10 | 557624745 |
| 11 | 15204727395 |
| 12 | 458112683787 |
| 13 | 15113457195837 |
| 14 | 541914801559313 |
| 15 | 20984168325697395 |
| 16 | 872681528769576675 |
| 17 | 38793582477781496685 |
| 18 | 1835683831177469267769 |
| 19 | 92124361183712633639235 |
| 20 | 4887330703061330205124475 |
[1,1,3,27,285,3585,56595,1062131,22868685, 557624745,15204727395,458112683787,15113457195837, 541914801559313,20984168325697395, 872681528769576675,38793582477781496685, 1835683831177469267769,92124361183712633639235, 4887330703061330205124475] |