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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 36 |
| 5 | 138 |
| 6 | 560 |
| 7 | 2402 |
| 8 | 10898 |
| 9 | 52392 |
| 10 | 267394 |
| 11 | 1450790 |
| 12 | 8371220 |
| 13 | 51327178 |
| 14 | 333759746 |
| 15 | 2295276480 |
| 16 | 16639104002 |
| 17 | 126718172670 |
| 18 | 1010487248556 |
| 19 | 8411744415418 |
| 20 | 72899055533482 |
| 21 | 656136245454232 |
| 22 | 6120474697035762 |
[1,1,3,10,36,138,560,2402,10898,52392,267394, 1450790,8371220,51327178,333759746,2295276480, 16639104002,126718172670,1010487248556, 8411744415418,72899055533482,656136245454232, 6120474697035762] |