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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 8 |
| 6 | 19 |
| 7 | 48 |
| 8 | 120 |
| 9 | 320 |
| 10 | 864 |
| 11 | 2372 |
| 12 | 6581 |
| 13 | 18470 |
| 14 | 52094 |
| 15 | 147966 |
| 16 | 421931 |
| 17 | 1208214 |
| 18 | 3470789 |
| 19 | 10001186 |
| 20 | 28892674 |
| 21 | 83671476 |
| 22 | 242823392 |
| 23 | 706090582 |
| 24 | 2056861981 |
| 25 | 6001601254 |
| 26 | 17538308071 |
| 27 | 51323923796 |
| 28 | 150389970179 |
| 29 | 441211039118 |
| 30 | 1295886198194 |
| 31 | 3810209524640 |
| 32 | 11214075937205 |
| 33 | 33035791339150 |
[2,1,2,4,8,19,48,120,320,864,2372,6581,18470, 52094,147966,421931,1208214,3470789,10001186, 28892674,83671476,242823392,706090582,2056861981, 6001601254,17538308071,51323923796,150389970179, 441211039118,1295886198194,3810209524640, 11214075937205,33035791339150] |