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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 85 |
| 6 | 420 |
| 7 | 2443 |
| 8 | 16136 |
| 9 | 120222 |
| 10 | 993770 |
| 11 | 9042451 |
| 12 | 89725944 |
| 13 | 964693717 |
| 14 | 11168801294 |
| 15 | 138549935190 |
| 16 | 1833264311504 |
| 17 | 25773751694161 |
| 18 | 383664263687964 |
| 19 | 6028473673565695 |
| 20 | 99710105438401940 |
| 21 | 1731651866118338766 |
| 22 | 31505416776034601510 |
| 23 | 599259743707431667279 |
[1,1,2,6,20,85,420,2443,16136,120222,993770, 9042451,89725944,964693717,11168801294, 138549935190,1833264311504,25773751694161, 383664263687964,6028473673565695, 99710105438401940,1731651866118338766, 31505416776034601510,599259743707431667279] |