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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 22 |
| 5 | 70 |
| 6 | 265 |
| 7 | 1007 |
| 8 | 4055 |
| 9 | 16593 |
| 10 | 69429 |
| 11 | 294509 |
| 12 | 1265692 |
| 13 | 5494398 |
| 14 | 24065829 |
| 15 | 106207739 |
| 16 | 471840078 |
| 17 | 2108406146 |
| 18 | 9470071142 |
| 19 | 42731427358 |
| 20 | 193612759011 |
| 21 | 880517540867 |
[1,3,6,22,70,265,1007,4055,16593,69429,294509, 1265692,5494398,24065829,106207739,471840078, 2108406146,9470071142,42731427358,193612759011, 880517540867] |