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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 25 |
| 6 | 108 |
| 7 | 492 |
| 8 | 2431 |
| 9 | 12371 |
| 10 | 65169 |
| 11 | 350792 |
| 12 | 1926372 |
| 13 | 10744924 |
| 14 | 60762760 |
| 15 | 347653944 |
| 16 | 2009690895 |
| 17 | 11723100775 |
| 18 | 68937782355 |
| 19 | 408323229930 |
| 20 | 2434289046255 |
| 21 | 14598011263089 |
| 22 | 88011196469040 |
| 23 | 533216750567280 |
| 24 | 3245004785069892 |
| 25 | 19829768942544276 |
| 26 | 121639211516546668 |
[1,1,1,2,7,25,108,492,2431,12371,65169,350792, 1926372,10744924,60762760,347653944,2009690895, 11723100775,68937782355,408323229930, 2434289046255,14598011263089,88011196469040, 533216750567280,3245004785069892, 19829768942544276,121639211516546668] |