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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 117 |
| 4 | 1257 |
| 5 | 17163 |
| 6 | 284055 |
| 7 | 5522877 |
| 8 | 123344817 |
| 9 | 3111071283 |
| 10 | 87454712895 |
| 11 | 2710961144037 |
| 12 | 91862770847577 |
| 13 | 3378032307195003 |
| 14 | 133970268354806535 |
| 15 | 5699864583381903597 |
| 16 | 258956671286986317537 |
| 17 | 12512342291081486212323 |
| 18 | 640686944845321006836975 |
[1,3,15,117,1257,17163,284055,5522877,123344817, 3111071283,87454712895,2710961144037, 91862770847577,3378032307195003, 133970268354806535,5699864583381903597, 258956671286986317537,12512342291081486212323, 640686944845321006836975] |