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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 217 |
| 5 | 3206 |
| 6 | 59000 |
| 7 | 1288184 |
| 8 | 32391811 |
| 9 | 919625298 |
| 10 | 29062669744 |
| 11 | 1011423361344 |
| 12 | 38432306102230 |
| 13 | 1583371370586372 |
| 14 | 70311532983998416 |
| 15 | 3348279599587251984 |
| 16 | 170232740676793931347 |
| 17 | 9204327574128495048866 |
[1,1,3,20,217,3206,59000,1288184,32391811, 919625298,29062669744,1011423361344, 38432306102230,1583371370586372,70311532983998416, 3348279599587251984,170232740676793931347, 9204327574128495048866] |