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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 119 |
| 6 | 700 |
| 7 | 4748 |
| 8 | 36403 |
| 9 | 310851 |
| 10 | 2922606 |
| 11 | 29977587 |
| 12 | 332929492 |
| 13 | 3978258079 |
| 14 | 50872884285 |
| 15 | 692985674373 |
| 16 | 10015172966221 |
| 17 | 153021613683924 |
| 18 | 2464031776132958 |
| 19 | 41698912656882644 |
| 20 | 739771703127828419 |
| 21 | 13727160292457369098 |
| 22 | 265876635231121617716 |
[1,1,2,6,24,119,700,4748,36403,310851,2922606, 29977587,332929492,3978258079,50872884285, 692985674373,10015172966221,153021613683924, 2464031776132958,41698912656882644, 739771703127828419,13727160292457369098, 265876635231121617716] |