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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 5 |
| 7 | 17 |
| 8 | 37 |
| 9 | 107 |
| 10 | 651 |
| 11 | 4763 |
| 12 | 31885 |
| 13 | 243507 |
| 14 | 2726593 |
| 15 | 39573223 |
| 16 | 647861719 |
| 17 | 12294997893 |
| 18 | 299566536047 |
| 19 | 9265546813073 |
| 20 | 344823799726629 |
[1,1,1,1,1,5,17,37,107,651,4763,31885,243507, 2726593,39573223,647861719,12294997893, 299566536047,9265546813073,344823799726629] |