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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 7 |
| 4 | 27 |
| 5 | 121 |
| 6 | 553 |
| 7 | 3865 |
| 8 | 24625 |
| 9 | 202954 |
| 10 | 1519540 |
| 11 | 14193455 |
| 12 | 132441998 |
| 13 | 1381539355 |
| 14 | 14096067555 |
| 15 | 168745220585 |
| 16 | 1961128020387 |
| 17 | 25473872598375 |
| 18 | 324797436024684 |
| 19 | 4647784901400988 |
| 20 | 65394584337577858 |
| 21 | 1012005650484163962 |
| 22 | 15285115573675197704 |
[0,1,1,7,27,121,553,3865,24625,202954,1519540, 14193455,132441998,1381539355,14096067555, 168745220585,1961128020387,25473872598375, 324797436024684,4647784901400988, 65394584337577858,1012005650484163962, 15285115573675197704] |