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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 18 |
| 5 | 41 |
| 6 | 82 |
| 7 | 188 |
| 8 | 376 |
| 9 | 867 |
| 10 | 1734 |
| 11 | 4020 |
| 12 | 8040 |
| 13 | 18735 |
| 14 | 37470 |
| 15 | 87735 |
| 16 | 175470 |
| 17 | 412715 |
| 18 | 825430 |
| 19 | 1949624 |
| 20 | 3899248 |
| 21 | 9245721 |
| 22 | 18491442 |
| 23 | 44003717 |
| 24 | 88007434 |
| 25 | 210121733 |
| 26 | 420243466 |
| 27 | 1006390014 |
| 28 | 2012780028 |
| 29 | 4833517551 |
[1,2,4,9,18,41,82,188,376,867,1734,4020,8040, 18735,37470,87735,175470,412715,825430,1949624, 3899248,9245721,18491442,44003717,88007434, 210121733,420243466,1006390014,2012780028, 4833517551] |