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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 56 |
| 5 | 211 |
| 6 | 1025 |
| 7 | 4307 |
| 8 | 21204 |
| 9 | 94266 |
| 10 | 467078 |
| 11 | 2145817 |
| 12 | 10669555 |
| 13 | 50053958 |
| 14 | 249384307 |
| 15 | 1186640955 |
| 16 | 5919439517 |
| 17 | 28450917045 |
| 18 | 142033418623 |
| 19 | 687720200014 |
| 20 | 3434955791348 |
| 21 | 16724912981263 |
| 22 | 83563256781361 |
| 23 | 408630153079305 |
| 24 | 2042102527291284 |
| 25 | 10020026867440662 |
| 26 | 50081965879762276 |
| 27 | 246408793434070306 |
[1,1,4,12,56,211,1025,4307,21204,94266,467078, 2145817,10669555,50053958,249384307,1186640955, 5919439517,28450917045,142033418623,687720200014, 3434955791348,16724912981263,83563256781361, 408630153079305,2042102527291284, 10020026867440662,50081965879762276, 246408793434070306] |