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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 1 |
| 7 | 5 |
| 8 | 19 |
| 9 | 37 |
| 10 | 77 |
| 11 | 131 |
| 12 | 515 |
| 13 | 1575 |
| 14 | 6459 |
| 15 | 26455 |
| 16 | 139873 |
| 17 | 647697 |
| 18 | 4036849 |
| 19 | 21133021 |
| 20 | 162531941 |
| 21 | 1088442077 |
[1,1,1,1,1,1,5,19,37,77,131,515,1575,6459,26455, 139873,647697,4036849,21133021,162531941, 1088442077] |