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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 21 |
| 4 | 181 |
| 5 | 1746 |
| 6 | 18039 |
| 7 | 195214 |
| 8 | 2184381 |
| 9 | 25067856 |
| 10 | 293420578 |
| 11 | 3489516381 |
| 12 | 42044519283 |
| 13 | 512146618088 |
| 14 | 6296546349018 |
| 15 | 78031090301868 |
| 16 | 973723814391957 |
| 17 | 12224652295383324 |
| 18 | 154299365902579044 |
| 19 | 1956876044969421604 |
| 20 | 24924046596321581940 |
[1,1,3,21,181,1746,18039,195214,2184381,25067856, 293420578,3489516381,42044519283,512146618088, 6296546349018,78031090301868,973723814391957, 12224652295383324,154299365902579044, 1956876044969421604,24924046596321581940] |