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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 27 |
| 7 | 80 |
| 8 | 255 |
| 9 | 870 |
| 10 | 3155 |
| 11 | 12100 |
| 12 | 48871 |
| 13 | 207162 |
| 14 | 918944 |
| 15 | 4254690 |
| 16 | 20513838 |
| 17 | 102784942 |
| 18 | 534205629 |
| 19 | 2875098840 |
| 20 | 15999114433 |
| 21 | 91923562922 |
| 22 | 544606671776 |
| 23 | 3323112062994 |
| 24 | 20860869818386 |
| 25 | 134585869671342 |
[1,1,1,2,4,10,27,80,255,870,3155,12100,48871, 207162,918944,4254690,20513838,102784942, 534205629,2875098840,15999114433,91923562922, 544606671776,3323112062994,20860869818386, 134585869671342] |