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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 27 |
| 3 | 104 |
| 4 | 366 |
| 5 | 1212 |
| 6 | 3842 |
| 7 | 11784 |
| 8 | 35223 |
| 9 | 103122 |
| 10 | 296805 |
| 11 | 842160 |
| 12 | 2360780 |
| 13 | 6549240 |
| 14 | 18004980 |
| 15 | 49106992 |
| 16 | 132996957 |
| 17 | 357948894 |
| 18 | 957993823 |
| 19 | 2550977112 |
| 20 | 6761742234 |
| 21 | 17848312884 |
| 22 | 46932923478 |
| 23 | 122980461816 |
[1,6,27,104,366,1212,3842,11784,35223,103122, 296805,842160,2360780,6549240,18004980,49106992, 132996957,357948894,957993823,2550977112, 6761742234,17848312884,46932923478,122980461816] |