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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 22 |
| 6 | 56 |
| 7 | 147 |
| 8 | 396 |
| 9 | 1088 |
| 10 | 3036 |
| 11 | 8582 |
| 12 | 24524 |
| 13 | 70727 |
| 14 | 205594 |
| 15 | 601756 |
| 16 | 1771937 |
| 17 | 5245544 |
| 18 | 15602496 |
| 19 | 46606356 |
| 20 | 139753120 |
| 21 | 420520000 |
| 22 | 1269361000 |
| 23 | 3842722454 |
| 24 | 11663928644 |
| 25 | 35490451807 |
| 26 | 108232655126 |
| 27 | 330760284892 |
[1,2,4,9,22,56,147,396,1088,3036,8582,24524,70727, 205594,601756,1771937,5245544,15602496,46606356, 139753120,420520000,1269361000,3842722454, 11663928644,35490451807,108232655126,330760284892] |