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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 55 |
| 5 | 622 |
| 6 | 8015 |
| 7 | 113164 |
| 8 | 1711898 |
| 9 | 27357970 |
| 10 | 457507917 |
| 11 | 7952476482 |
| 12 | 142972019125 |
| 13 | 2648639456048 |
| 14 | 50415218306637 |
| 15 | 983728646223556 |
| 16 | 19641163430509505 |
| 17 | 400671660024507294 |
| 18 | 8340743906266061866 |
| 19 | 176998642509849677206 |
| 20 | 3825680705425292568049 |
| 21 | 84159282700462688412042 |
[1,1,6,55,622,8015,113164,1711898,27357970, 457507917,7952476482,142972019125,2648639456048, 50415218306637,983728646223556,19641163430509505, 400671660024507294,8340743906266061866, 176998642509849677206,3825680705425292568049, 84159282700462688412042] |