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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 28 |
| 6 | 108 |
| 7 | 507 |
| 8 | 2431 |
| 9 | 12441 |
| 10 | 65169 |
| 11 | 351156 |
| 12 | 1926372 |
| 13 | 10746856 |
| 14 | 60762760 |
| 15 | 347664603 |
| 16 | 2009690895 |
| 17 | 11723160835 |
| 18 | 68937782355 |
| 19 | 408323575275 |
| 20 | 2434289046255 |
| 21 | 14598013278960 |
| 22 | 88011196469040 |
| 23 | 533216762488020 |
| 24 | 3245004785069892 |
| 25 | 19829769013792908 |
[1,1,1,3,7,28,108,507,2431,12441,65169,351156, 1926372,10746856,60762760,347664603,2009690895, 11723160835,68937782355,408323575275, 2434289046255,14598013278960,88011196469040, 533216762488020,3245004785069892, 19829769013792908] |