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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 81 |
| 5 | 331 |
| 6 | 1405 |
| 7 | 6134 |
| 8 | 27331 |
| 9 | 123742 |
| 10 | 567304 |
| 11 | 2627172 |
| 12 | 12267169 |
| 13 | 57671808 |
| 14 | 272693750 |
| 15 | 1295686844 |
| 16 | 6182107658 |
| 17 | 29603230521 |
| 18 | 142201981662 |
| 19 | 684965998290 |
| 20 | 3307416586384 |
| 21 | 16004684113039 |
| 22 | 77596661917609 |
| 23 | 376869159163474 |
| 24 | 1833224367856779 |
| 25 | 8930048599783207 |
| 26 | 43556122332636789 |
| 27 | 212692776891161612 |
[1,2,6,21,81,331,1405,6134,27331,123742,567304, 2627172,12267169,57671808,272693750,1295686844, 6182107658,29603230521,142201981662,684965998290, 3307416586384,16004684113039,77596661917609, 376869159163474,1833224367856779,8930048599783207, 43556122332636789,212692776891161612] |