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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 73 |
| 5 | 466 |
| 6 | 3309 |
| 7 | 25425 |
| 8 | 209717 |
| 9 | 1837168 |
| 10 | 16995545 |
| 11 | 164906160 |
| 12 | 1671977735 |
| 13 | 17635855420 |
| 14 | 193014602116 |
| 15 | 2185071349740 |
| 16 | 25536219128057 |
| 17 | 307379906553394 |
| 18 | 3804874686396912 |
| 19 | 48350298542927709 |
| 20 | 629940434070025851 |
[1,1,3,13,73,466,3309,25425,209717,1837168, 16995545,164906160,1671977735,17635855420, 193014602116,2185071349740,25536219128057, 307379906553394,3804874686396912, 48350298542927709,629940434070025851] |