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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 4 |
| 7 | 6 |
| 8 | 19 |
| 9 | 49 |
| 10 | 150 |
| 11 | 442 |
| 12 | 1424 |
| 13 | 4522 |
| 14 | 14924 |
| 15 | 49536 |
| 16 | 167367 |
| 17 | 570285 |
| 18 | 1965058 |
| 19 | 6823410 |
| 20 | 23884366 |
| 21 | 84155478 |
| 22 | 298377508 |
| 23 | 1063750740 |
| 24 | 3811803164 |
| 25 | 13722384546 |
| 26 | 49611801980 |
| 27 | 180072089896 |
| 28 | 655977266884 |
| 29 | 2397708652276 |
| 30 | 8791599732140 |
| 31 | 32330394085528 |
[1,1,1,1,4,6,19,49,150,442,1424,4522,14924,49536, 167367,570285,1965058,6823410,23884366,84155478, 298377508,1063750740,3811803164,13722384546, 49611801980,180072089896,655977266884, 2397708652276,8791599732140,32330394085528] |