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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 9 |
| 5 | 22 |
| 6 | 55 |
| 7 | 153 |
| 8 | 431 |
| 9 | 1235 |
| 10 | 3555 |
| 11 | 10278 |
| 12 | 29793 |
| 13 | 86562 |
| 14 | 251983 |
| 15 | 734776 |
| 16 | 2145825 |
| 17 | 6275148 |
| 18 | 18373299 |
| 19 | 53856156 |
| 20 | 158025189 |
| 21 | 464112300 |
| 22 | 1364247183 |
| 23 | 4013353935 |
| 24 | 11815188003 |
| 25 | 34807249137 |
| 26 | 102606325139 |
| 27 | 302646363728 |
| 28 | 893175905781 |
[1,3,6,9,22,55,153,431,1235,3555,10278,29793, 86562,251983,734776,2145825,6275148,18373299, 53856156,158025189,464112300,1364247183, 4013353935,11815188003,34807249137,102606325139, 302646363728,893175905781] |