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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 20 |
| 5 | 54 |
| 6 | 197 |
| 7 | 606 |
| 8 | 2327 |
| 9 | 7790 |
| 10 | 31007 |
| 11 | 109983 |
| 12 | 449032 |
| 13 | 1661627 |
| 14 | 6916014 |
| 15 | 26432615 |
| 16 | 111689208 |
| 17 | 437872815 |
| 18 | 1872854711 |
| 19 | 7494986572 |
| 20 | 32380670287 |
| 21 | 131800276738 |
| 22 | 574239393129 |
| 23 | 2370817824876 |
| 24 | 10403919136964 |
| 25 | 43476364103039 |
| 26 | 191976353694999 |
| 27 | 810631010434670 |
| 28 | 3598904531548287 |
[1,1,3,6,20,54,197,606,2327,7790,31007,109983, 449032,1661627,6916014,26432615,111689208, 437872815,1872854711,7494986572,32380670287, 131800276738,574239393129,2370817824876, 10403919136964,43476364103039,191976353694999, 810631010434670,3598904531548287] |