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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 32 |
| 5 | 117 |
| 6 | 460 |
| 7 | 1850 |
| 8 | 7680 |
| 9 | 32467 |
| 10 | 139631 |
| 11 | 608280 |
| 12 | 2679881 |
| 13 | 11916492 |
| 14 | 53417407 |
| 15 | 241118245 |
| 16 | 1095030281 |
| 17 | 4999847240 |
| 18 | 22938576846 |
| 19 | 105690791104 |
| 20 | 488860041249 |
| 21 | 2269080989966 |
| 22 | 10565660913109 |
| 23 | 49340702712984 |
| 24 | 231031730790560 |
[1,1,3,9,32,117,460,1850,7680,32467,139631,608280, 2679881,11916492,53417407,241118245,1095030281, 4999847240,22938576846,105690791104,488860041249, 2269080989966,10565660913109,49340702712984, 231031730790560] |