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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 14 |
| 4 | 55 |
| 5 | 252 |
| 6 | 1319 |
| 7 | 7737 |
| 8 | 50040 |
| 9 | 351636 |
| 10 | 2659375 |
| 11 | 21519027 |
| 12 | 185279186 |
| 13 | 1688183135 |
| 14 | 16206401020 |
| 15 | 163376811610 |
| 16 | 1724624368377 |
| 17 | 19011582728772 |
| 18 | 218312877627483 |
| 19 | 2605840967052663 |
| 20 | 32271957793959066 |
| 21 | 413991491885677105 |
| 22 | 5492584623675060620 |
[1,1,4,14,55,252,1319,7737,50040,351636,2659375, 21519027,185279186,1688183135,16206401020, 163376811610,1724624368377,19011582728772, 218312877627483,2605840967052663, 32271957793959066,413991491885677105, 5492584623675060620] |