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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 111 |
| 6 | 540 |
| 7 | 2736 |
| 8 | 14396 |
| 9 | 77649 |
| 10 | 427608 |
| 11 | 2392866 |
| 12 | 13570386 |
| 13 | 77815161 |
| 14 | 450418536 |
| 15 | 2628225684 |
| 16 | 15443406868 |
| 17 | 91301938365 |
| 18 | 542704450806 |
| 19 | 3241411991712 |
| 20 | 19443499011192 |
| 21 | 117084197728737 |
| 22 | 707532791560272 |
| 23 | 4289252607915012 |
| 24 | 26078561954153631 |
[1,2,6,25,111,540,2736,14396,77649,427608,2392866, 13570386,77815161,450418536,2628225684, 15443406868,91301938365,542704450806, 3241411991712,19443499011192,117084197728737, 707532791560272,4289252607915012, 26078561954153631] |