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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 28 |
| 4 | 91 |
| 5 | 302 |
| 6 | 1021 |
| 7 | 3507 |
| 8 | 12209 |
| 9 | 42991 |
| 10 | 152866 |
| 11 | 548148 |
| 12 | 1979990 |
| 13 | 7198055 |
| 14 | 26316577 |
| 15 | 96701545 |
| 16 | 356941485 |
| 17 | 1322891115 |
| 18 | 4920919230 |
| 19 | 18366138480 |
| 20 | 68756266170 |
| 21 | 258118218960 |
| 22 | 971492416674 |
| 23 | 3665120443878 |
| 24 | 13857614540714 |
[1,3,9,28,91,302,1021,3507,12209,42991,152866, 548148,1979990,7198055,26316577,96701545, 356941485,1322891115,4920919230,18366138480, 68756266170,258118218960,971492416674, 3665120443878,13857614540714] |