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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 6 |
| 3 | 7 |
| 4 | 15 |
| 5 | 25 |
| 6 | 51 |
| 7 | 126 |
| 8 | 171 |
| 9 | 311 |
| 10 | 358 |
| 11 | 865 |
| 12 | 1850 |
| 13 | 3311 |
| 14 | 4686 |
| 15 | 7893 |
| 16 | 8249 |
| 17 | 17795 |
| 18 | 27176 |
| 19 | 48728 |
[4,6,7,15,25,51,126,171,311,358,865,1850,3311, 4686,7893,8249,17795,27176,48728] |