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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 9 |
| 6 | 22 |
| 7 | 59 |
| 8 | 165 |
| 9 | 496 |
| 10 | 1540 |
| 11 | 4960 |
| 12 | 16390 |
| 13 | 55408 |
| 14 | 190572 |
| 15 | 665699 |
| 16 | 2354932 |
| 17 | 8424025 |
| 18 | 30424768 |
| 19 | 110823984 |
| 20 | 406734060 |
| 21 | 1502876903 |
| 22 | 5586976572 |
| 23 | 20884546416 |
| 24 | 78460794158 |
| 25 | 296124542120 |
| 26 | 1122346648913 |
| 27 | 4270387848473 |
[1,1,1,2,4,9,22,59,165,496,1540,4960,16390,55408, 190572,665699,2354932,8424025,30424768,110823984, 406734060,1502876903,5586976572,20884546416, 78460794158,296124542120,1122346648913, 4270387848473] |