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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 63 |
| 5 | 217 |
| 6 | 822 |
| 7 | 3042 |
| 8 | 12073 |
| 9 | 46756 |
| 10 | 191331 |
| 11 | 764383 |
| 12 | 3196583 |
| 13 | 13064986 |
| 14 | 55529435 |
| 15 | 230948432 |
| 16 | 994032777 |
| 17 | 4191650602 |
| 18 | 18224285458 |
| 19 | 77714819878 |
| 20 | 340690355325 |
| 21 | 1466403984890 |
| 22 | 6473061148864 |
| 23 | 28081108273621 |
| 24 | 124685793447785 |
| 25 | 544555483915367 |
| 26 | 2430162878129049 |
| 27 | 10675588779615415 |
[1,2,6,18,63,217,822,3042,12073,46756,191331, 764383,3196583,13064986,55529435,230948432, 994032777,4191650602,18224285458,77714819878, 340690355325,1466403984890,6473061148864, 28081108273621,124685793447785,544555483915367, 2430162878129049,10675588779615415] |