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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 1 |
| 7 | 1 |
| 8 | 3 |
| 9 | 7 |
| 10 | 15 |
| 11 | 31 |
| 12 | 63 |
| 13 | 167 |
| 14 | 435 |
| 15 | 1337 |
| 16 | 5021 |
| 17 | 19355 |
| 18 | 85901 |
| 19 | 388093 |
| 20 | 1971221 |
| 21 | 10932161 |
[1,1,1,1,1,1,1,3,7,15,31,63,167,435,1337,5021, 19355,85901,388093,1971221,10932161] |