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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 24 |
| 5 | 74 |
| 6 | 245 |
| 7 | 815 |
| 8 | 2796 |
| 9 | 9707 |
| 10 | 34186 |
| 11 | 121562 |
| 12 | 436298 |
| 13 | 1577310 |
| 14 | 5740299 |
| 15 | 21008777 |
| 16 | 77279892 |
| 17 | 285544700 |
| 18 | 1059332082 |
| 19 | 3944254118 |
| 20 | 14734260864 |
| 21 | 55207053787 |
| 22 | 207421476390 |
| 23 | 781283558998 |
| 24 | 2949675307082 |
| 25 | 11160264942376 |
| 26 | 42309912978708 |
| 27 | 160700303600030 |
[1,1,3,8,24,74,245,815,2796,9707,34186,121562, 436298,1577310,5740299,21008777,77279892, 285544700,1059332082,3944254118,14734260864, 55207053787,207421476390,781283558998, 2949675307082,11160264942376,42309912978708, 160700303600030] |