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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 10 |
| 3 | 24 |
| 4 | 68 |
| 5 | 198 |
| 6 | 594 |
| 7 | 1816 |
| 8 | 5650 |
| 9 | 17824 |
| 10 | 56836 |
| 11 | 182788 |
| 12 | 592060 |
| 13 | 1929676 |
| 14 | 6323418 |
| 15 | 20819284 |
| 16 | 68828316 |
| 17 | 228372578 |
| 18 | 760188362 |
| 19 | 2537770576 |
| 20 | 8494004948 |
[6,10,24,68,198,594,1816,5650,17824,56836,182788, 592060,1929676,6323418,20819284,68828316, 228372578,760188362,2537770576,8494004948] |