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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 11 |
| 3 | 33 |
| 4 | 96 |
| 5 | 280 |
| 6 | 818 |
| 7 | 2387 |
| 8 | 6970 |
| 9 | 20347 |
| 10 | 59401 |
| 11 | 173414 |
| 12 | 506261 |
| 13 | 1477968 |
| 14 | 4314748 |
| 15 | 12596384 |
| 16 | 36773617 |
| 17 | 107356118 |
| 18 | 313413177 |
| 19 | 914971789 |
| 20 | 2671149257 |
| 21 | 7798096555 |
| 22 | 22765597881 |
| 23 | 66461404174 |
| 24 | 194026015382 |
| 25 | 566435438933 |
| 26 | 1653639620681 |
| 27 | 4827600476829 |
[1,4,11,33,96,280,818,2387,6970,20347,59401, 173414,506261,1477968,4314748,12596384,36773617, 107356118,313413177,914971789,2671149257, 7798096555,22765597881,66461404174,194026015382, 566435438933,1653639620681,4827600476829] |