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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 7 |
| 5 | 31 |
| 6 | 91 |
| 7 | 211 |
| 8 | 1681 |
| 9 | 12097 |
| 10 | 57961 |
| 11 | 209881 |
| 12 | 1874071 |
| 13 | 17842111 |
| 14 | 117303187 |
| 15 | 575683291 |
| 16 | 5691897121 |
| 17 | 65641390081 |
| 18 | 544238393041 |
| 19 | 3362783785777 |
| 20 | 36455473647271 |
| 21 | 485442581801311 |
| 22 | 4828464958268491 |
| 23 | 35900587138847971 |
[1,1,1,1,7,31,91,211,1681,12097,57961,209881, 1874071,17842111,117303187,575683291,5691897121, 65641390081,544238393041,3362783785777, 36455473647271,485442581801311,4828464958268491, 35900587138847971] |