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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 51 |
| 6 | 271 |
| 7 | 1366 |
| 8 | 8849 |
| 9 | 58717 |
| 10 | 432541 |
| 11 | 3530176 |
| 12 | 29787781 |
| 13 | 279974839 |
| 14 | 2715912291 |
| 15 | 28415168146 |
| 16 | 312503079841 |
| 17 | 3600714035321 |
| 18 | 43979791574809 |
| 19 | 556150585730140 |
| 20 | 7417561518005341 |
| 21 | 102438949373356891 |
| 22 | 1476634705941320311 |
| 23 | 22102618328057267694 |
[1,1,1,4,13,51,271,1366,8849,58717,432541,3530176, 29787781,279974839,2715912291,28415168146, 312503079841,3600714035321,43979791574809, 556150585730140,7417561518005341, 102438949373356891,1476634705941320311, 22102618328057267694] |