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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 8 |
| 4 | 52 |
| 5 | 224 |
| 6 | 1131 |
| 7 | 4620 |
| 8 | 23456 |
| 9 | 92752 |
| 10 | 460170 |
| 11 | 1805760 |
| 12 | 8946216 |
| 13 | 34942176 |
| 14 | 172593267 |
| 15 | 673129380 |
| 16 | 3323413216 |
| 17 | 12954246368 |
| 18 | 63944790462 |
| 19 | 249263001360 |
| 20 | 1230668687000 |
| 21 | 4798770328960 |
| 22 | 23700302314238 |
| 23 | 92457112946968 |
| 24 | 456814709763456 |
| 25 | 1782991313610720 |
| 26 | 8813232700137268 |
[1,8,52,224,1131,4620,23456,92752,460170,1805760, 8946216,34942176,172593267,673129380,3323413216, 12954246368,63944790462,249263001360, 1230668687000,4798770328960,23700302314238, 92457112946968,456814709763456,1782991313610720, 8813232700137268] |