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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 15 |
| 4 | 63 |
| 5 | 217 |
| 6 | 999 |
| 7 | 3757 |
| 8 | 17793 |
| 9 | 69809 |
| 10 | 334365 |
| 11 | 1361721 |
| 12 | 6570421 |
| 13 | 27323139 |
| 14 | 132784185 |
| 15 | 561952215 |
| 16 | 2743176341 |
| 17 | 11766979961 |
| 18 | 57626807759 |
| 19 | 249837943569 |
| 20 | 1226981605029 |
| 21 | 5366122994625 |
| 22 | 26411834991123 |
| 23 | 116363366768863 |
| 24 | 573725892578869 |
| 25 | 2543389304313541 |
| 26 | 12558714178737849 |
| 27 | 55970650933680377 |
[1,1,5,15,63,217,999,3757,17793,69809,334365, 1361721,6570421,27323139,132784185,561952215, 2743176341,11766979961,57626807759,249837943569, 1226981605029,5366122994625,26411834991123, 116363366768863,573725892578869,2543389304313541, 12558714178737849,55970650933680377] |