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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 18 |
| 5 | 70 |
| 6 | 282 |
| 7 | 1189 |
| 8 | 5144 |
| 9 | 22804 |
| 10 | 102908 |
| 11 | 471477 |
| 12 | 2186648 |
| 13 | 10247609 |
| 14 | 48449798 |
| 15 | 230819691 |
| 16 | 1106961890 |
| 17 | 5339801036 |
| 18 | 25891658674 |
| 19 | 126123321469 |
| 20 | 616916700222 |
| 21 | 3028854625890 |
| 22 | 14921089624916 |
| 23 | 73733085073247 |
| 24 | 365384562116904 |
| 25 | 1815365194118833 |
[0,1,2,5,18,70,282,1189,5144,22804,102908,471477, 2186648,10247609,48449798,230819691,1106961890, 5339801036,25891658674,126123321469,616916700222, 3028854625890,14921089624916,73733085073247, 365384562116904,1815365194118833] |