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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 75 |
| 6 | 259 |
| 7 | 853 |
| 8 | 2684 |
| 9 | 8120 |
| 10 | 23782 |
| 11 | 67845 |
| 12 | 189493 |
| 13 | 520359 |
| 14 | 1409742 |
| 15 | 3778514 |
| 16 | 10042552 |
| 17 | 26517095 |
| 18 | 69668495 |
| 19 | 182357337 |
| 20 | 476027280 |
| 21 | 1240285036 |
| 22 | 3227591882 |
| 23 | 8393207561 |
| 24 | 21819385961 |
| 25 | 56722065995 |
| 26 | 147485931154 |
| 27 | 383621798278 |
| 28 | 998279190044 |
| 29 | 2599085844715 |
| 30 | 6770473854147 |
| 31 | 17646032160125 |
[1,1,2,6,21,75,259,853,2684,8120,23782,67845, 189493,520359,1409742,3778514,10042552,26517095, 69668495,182357337,476027280,1240285036, 3227591882,8393207561,21819385961,56722065995, 147485931154,383621798278,998279190044, 2599085844715,6770473854147,17646032160125] |