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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 9 |
| 3 | 42 |
| 4 | 178 |
| 5 | 910 |
| 6 | 4212 |
| 7 | 19899 |
| 8 | 94217 |
| 9 | 445859 |
| 10 | 2113257 |
| 11 | 10006598 |
| 12 | 47387904 |
| 13 | 224418390 |
| 14 | 1062810762 |
| 15 | 5033385029 |
| 16 | 23837475807 |
| 17 | 112891241315 |
| 18 | 534638647159 |
| 19 | 2531982065694 |
| 20 | 11991154349342 |
| 21 | 56788620500294 |
| 22 | 268943860673076 |
[3,9,42,178,910,4212,19899,94217,445859,2113257, 10006598,47387904,224418390,1062810762,5033385029, 23837475807,112891241315,534638647159, 2531982065694,11991154349342,56788620500294, 268943860673076] |