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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 15 |
| 4 | 41 |
| 5 | 106 |
| 6 | 284 |
| 7 | 750 |
| 8 | 2010 |
| 9 | 5382 |
| 10 | 14523 |
| 11 | 39290 |
| 12 | 106854 |
| 13 | 291552 |
| 14 | 798675 |
| 15 | 2194828 |
| 16 | 6051153 |
| 17 | 16730373 |
| 18 | 46383002 |
| 19 | 128910484 |
| 20 | 359115067 |
| 21 | 1002575810 |
| 22 | 2804667061 |
| 23 | 7860780578 |
| 24 | 22070885735 |
| 25 | 62071872704 |
| 26 | 174842835886 |
| 27 | 493217417610 |
[1,2,6,15,41,106,284,750,2010,5382,14523,39290, 106854,291552,798675,2194828,6051153,16730373, 46383002,128910484,359115067,1002575810, 2804667061,7860780578,22070885735,62071872704, 174842835886,493217417610] |