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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 20 |
| 5 | 54 |
| 6 | 189 |
| 7 | 594 |
| 8 | 2143 |
| 9 | 7387 |
| 10 | 27380 |
| 11 | 100067 |
| 12 | 379944 |
| 13 | 1443052 |
| 14 | 5599659 |
| 15 | 21844255 |
| 16 | 86394133 |
| 17 | 343768974 |
| 18 | 1381731518 |
| 19 | 5584666966 |
| 20 | 22751462847 |
| 21 | 93150610255 |
| 22 | 383799188075 |
| 23 | 1588579086014 |
| 24 | 6608521212364 |
| 25 | 27608162197782 |
| 26 | 115812839302734 |
| 27 | 487692262398236 |
| 28 | 2060876813337521 |
[1,1,3,6,20,54,189,594,2143,7387,27380,100067, 379944,1443052,5599659,21844255,86394133, 343768974,1381731518,5584666966,22751462847, 93150610255,383799188075,1588579086014, 6608521212364,27608162197782,115812839302734, 487692262398236,2060876813337521] |