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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 7 |
| 4 | 13 |
| 5 | 25 |
| 6 | 46 |
| 7 | 86 |
| 8 | 161 |
| 9 | 301 |
| 10 | 562 |
| 11 | 1051 |
| 12 | 1964 |
| 13 | 3670 |
| 14 | 6859 |
| 15 | 12819 |
| 16 | 23956 |
| 17 | 44772 |
| 18 | 83673 |
[1,2,4,7,13,25,46,86,161,301,562,1051,1964,3670, 6859,12819,23956,44772,83673] |