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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 63 |
| 5 | 521 |
| 6 | 5295 |
| 7 | 64048 |
| 8 | 907199 |
| 9 | 14717173 |
| 10 | 270429934 |
| 11 | 5561319631 |
| 12 | 126824201866 |
| 13 | 3183127838869 |
| 14 | 87328494060529 |
| 15 | 2604069098659922 |
| 16 | 83975195990867113 |
| 17 | 2915521294244073351 |
| 18 | 108553405498985038390 |
| 19 | 4319110373993534510736 |
| 20 | 183057722816741327269600 |
[1,1,2,10,63,521,5295,64048,907199,14717173, 270429934,5561319631,126824201866,3183127838869, 87328494060529,2604069098659922,83975195990867113, 2915521294244073351,108553405498985038390, 4319110373993534510736,183057722816741327269600] |