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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 3 |
| 7 | 13 |
| 8 | 31 |
| 9 | 85 |
| 10 | 391 |
| 11 | 2235 |
| 12 | 16087 |
| 13 | 124573 |
| 14 | 1136363 |
| 15 | 12958205 |
| 16 | 185857105 |
| 17 | 3266797811 |
| 18 | 68594033643 |
| 19 | 1733074438523 |
| 20 | 53263262779599 |
| 21 | 1999938243860711 |
[1,1,1,1,1,3,13,31,85,391,2235,16087,124573, 1136363,12958205,185857105,3266797811,68594033643, 1733074438523,53263262779599,1999938243860711] |