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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 17 |
| 5 | 45 |
| 6 | 117 |
| 7 | 305 |
| 8 | 798 |
| 9 | 2090 |
| 10 | 5473 |
| 11 | 14329 |
| 12 | 37513 |
| 13 | 98209 |
| 14 | 257114 |
| 15 | 673134 |
| 16 | 1762289 |
| 17 | 4613733 |
| 18 | 12078909 |
| 19 | 31622993 |
| 20 | 82790070 |
| 21 | 216747218 |
| 22 | 567451585 |
| 23 | 1485607537 |
| 24 | 3889371025 |
| 25 | 10182505537 |
| 26 | 26658145586 |
| 27 | 69791931222 |
| 28 | 182717648081 |
[1,1,2,6,17,45,117,305,798,2090,5473,14329,37513, 98209,257114,673134,1762289,4613733,12078909, 31622993,82790070,216747218,567451585,1485607537, 3889371025,10182505537,26658145586,69791931222, 182717648081] |