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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 3 |
| 7 | 13 |
| 8 | 31 |
| 9 | 77 |
| 10 | 387 |
| 11 | 2257 |
| 12 | 17627 |
| 13 | 156913 |
| 14 | 1449769 |
| 15 | 17078273 |
| 16 | 269362403 |
| 17 | 5270658519 |
| 18 | 128747962057 |
| 19 | 3752690933565 |
| 20 | 128409913359645 |
| 21 | 5451255918471683 |
[1,1,1,1,1,3,13,31,77,387,2257,17627,156913, 1449769,17078273,269362403,5270658519, 128747962057,3752690933565,128409913359645, 5451255918471683] |