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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 91 |
| 5 | 607 |
| 6 | 4298 |
| 7 | 31720 |
| 8 | 241321 |
| 9 | 1879097 |
| 10 | 14903013 |
| 11 | 119965086 |
| 12 | 977623639 |
| 13 | 8049579047 |
| 14 | 66864689674 |
| 15 | 559650696185 |
| 16 | 4715304229460 |
| 17 | 39960204165865 |
| 18 | 340395043021399 |
| 19 | 2912963919210012 |
| 20 | 25031055321749916 |
| 21 | 215894227588453950 |
| 22 | 1868403327770467149 |
[1,1,3,15,91,607,4298,31720,241321,1879097, 14903013,119965086,977623639,8049579047, 66864689674,559650696185,4715304229460, 39960204165865,340395043021399,2912963919210012, 25031055321749916,215894227588453950, 1868403327770467149] |