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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 26 |
| 6 | 154 |
| 7 | 1188 |
| 8 | 11474 |
| 9 | 134432 |
| 10 | 1863168 |
| 11 | 29936846 |
| 12 | 548625820 |
| 13 | 11315025894 |
| 14 | 259733293774 |
| 15 | 6574304470320 |
| 16 | 182050022755386 |
| 17 | 5477819548007438 |
| 18 | 178054691097463354 |
| 19 | 6220193033111607018 |
[1,1,1,2,6,26,154,1188,11474,134432,1863168, 29936846,548625820,11315025894,259733293774, 6574304470320,182050022755386,5477819548007438, 178054691097463354,6220193033111607018] |